Develop Reference

How to: Use DisplayManager to get displays and set a bool

My understanding of Java is basically nonexistent .. I only really understand Dart.
However, I need to use DisplayManager and getDisplays() in order to set a boolean.
I need something like this (I know this isn't really java, it's just so someone can get an understanding):
DisplayManager displayManager = DisplayManager();
List<Display> displays = [];
bool hasDisplays = false;
void _getDisplays(){
displays = DisplayManager.getDisplays();
}
void _displayBool(){
if(displays.length > 1){
hasDisplays = true;
} else {
hasDisplays = false;
}
if someone could show me how the hell I'm supposed to do something like that, inside of this, it would be amazing
public class MainActivity extends FlutterActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
}

You need to get the DisplayManager with the context.getSystemService() function. Then you get the list of Displays (Display[]) from the displayManager.getDisplays() function. Then if you want to know if there are one or more displays in the list, set the statement to the boolean.
DisplayManager displayManager = (DisplayManager) getApplicationContext().getSystemService(Context.DISPLAY_SERVICE);
Display[] displays = displayManager.getDisplays();
boolean hasDisplays = displays.length >= 1;

Well you can try this code:
class TestScreenCount {
public static void main(String[] args) {
GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice[] allScreens = env.getScreenDevices();
System.out.println(Arrays.toString(allScreens));
}
}
This will output the connected displays, for my case (I have an external screen and a laptop screen):
[X11GraphicsDevice[screen=0], X11GraphicsDevice[screen=1]]

how to call the output of a method in another Activity 's textview?

im programming an app to sort numbers and display the sorting process
after the input is sorted , a new button will be showen to display the selection sort steps in a new activity
[SelectionSort activity 1
I want the output of the function SelectionSortMethod in SelectionSortclass to be displayed in a new activity activity_Ssteps
SelectionSort.java :
public class SelectionSort extends AppCompatActivity {
EditText input;
EditText output;
Button Ssteps ;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_selection_sort);
input=findViewById(R.id.input);
output=findViewById(R.id.output);
Ssteps = findViewById(R.id.steps);
Ssteps.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v) {
Intent s = new Intent(SelectionSort.this, com.example.sorted.Ssteps.class);
startActivityForResult(s, 1);
}
});}
public void sortButtonPressed(View view){
String[] numberList = input.getText().toString().split(",");
Integer[] numbers = new Integer[numberList.length];
for (int i = 0; i < numberList.length; i++) {
numbers[i] = Integer.parseInt(numberList[i]);
}
SelectionSortmethod(numbers);
output.setText(Arrays.toString(numbers));
// if button "sort " is pressed , the button "view steps "will be displayed
Ssteps.setVisibility(View.VISIBLE);
}
}
public static void SelectionSortmethod (Integer[] arr)
{
// some code for sorting and showing the steps
}
Ssteps.java :
public class Ssteps extends AppCompatActivity {
TextView steps_text ;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_ssteps);
setTitle("selection sort steps ");
steps_text =findViewById(R.id.Stepstextview);
}
}

You can just use intent.extras like so:
Intent s = new Intent(SelectionSort.this, com.example.sorted.Ssteps.class);
s.putExtra("AnyID",YOURDATA);
startActivity(s);
And then in your Ssteps.class you can get the data using
the id like this:
String ss = getIntent.getExtra("AnyID"); //the id is the same as the other one above
steps_text.settext(ss);

Working with Intents like Youssof described is the way to go for small applications like yours. However as you progress in Android programming, you should definitely have a look at splitting your application in Fragments rather than Activities. They can use a Viewmodel, which makes sharing lots of data between screens much easier. Also Fragments can be use in androidx Navigation component, whos changing Fragments can be beautifully arranged in a UI. Very convenient for product reviews.

How to keep the MediaRouter running in background activity?

please I need your help after searching a lot without issues.
I have an demostration app to use an second screen attached to my device.
I have the source code of the app, they use the Mediarouter class and an class named LauncherSecondScreen extended from the Presentation class
I have tried to make the app as an service to keep runnig the app in background, but the mediarouter callback seems running only on the princpal thread ( I'm not sure I am just a beginner in android dev).
I have the full code of the app : there is two layout activity one showed on the princpal screen and the other on the second screen:
public class MainActivity extends Activity {
private final String TAG = "PresentationWithMediaRouterActivity";
private MediaRouter mMediaRouter;
private LauncherSecondScreen mPresentation;
private boolean mPaused;
/**
* Initialization of the Activity after it is first created. Must at least
* call {#link android.app.Activity#setContentView setContentView()} to
* describe what is to be displayed in the screen.
*/
#Override
protected void onCreate(Bundle savedInstanceState) {
// Be sure to call the super class.
super.onCreate(savedInstanceState);
// Get the media router service.
mMediaRouter = (MediaRouter)getSystemService(Context.MEDIA_ROUTER_SERVICE);
// See assets/res/any/layout/presentation_with_media_router_activity.xml for this
// view layout definition, which is being set here as
// the content of our screen.
setContentView(R.layout.activity_main);
}
#Override
protected void onResume() {
// Be sure to call the super class.
super.onResume();
// Listen for changes to media routes.
mMediaRouter.addCallback(MediaRouter.ROUTE_TYPE_LIVE_VIDEO, mMediaRouterCallback);
// Update the presentation based on the currently selected route.
mPaused = false;
updatePresentation();
}
private void updatePresentation() {
// Get the current route and its presentation display.
MediaRouter.RouteInfo route = mMediaRouter.getSelectedRoute(
MediaRouter.ROUTE_TYPE_LIVE_VIDEO);
Display presentationDisplay = route != null ? route.getPresentationDisplay() : null;
// Dismiss the current presentation if the display has changed.
if (mPresentation != null && mPresentation.getDisplay() != presentationDisplay) {
Log.i(TAG, "Dismissing presentation because the current route no longer "
+ "has a presentation display.");
mPresentation.dismiss();
mPresentation = null;
}
// Show a new presentation if needed.
if (mPresentation == null && presentationDisplay != null) {
Log.i(TAG, "Showing presentation on display: " + presentationDisplay);
mPresentation = new LauncherSecondScreen(this, presentationDisplay);
mPresentation.setOnDismissListener(mOnDismissListener);
try {
mPresentation.show();
} catch (WindowManager.InvalidDisplayException ex) {
Log.w(TAG, "Couldn't show presentation! Display was removed in "
+ "the meantime.", ex);
mPresentation = null;
}
}
// Update the contents playing in this activity.
updateContents();
}
private void updateContents() {
// Show either the content in the main activity or the content in the presentation
// along with some descriptive text about what is happening.
if (mPresentation != null) {
if (mPaused) {
mPresentation.dismiss();//getSurfaceView().onPause();
} else {
mPresentation.show();//getSurfaceView().onResume();
}
} else {
/* mInfoTextView.setText("presentation_with_media_router_now_playing_locally");
mSurfaceView.setVisibility(View.VISIBLE);
if (mPaused) {
mSurfaceView.onPause();
} else {
mSurfaceView.onResume();
}*/
}
}
private final MediaRouter.SimpleCallback mMediaRouterCallback =
new MediaRouter.SimpleCallback() {
#Override
public void onRouteSelected(MediaRouter router, int type, RouteInfo info) {
Log.d(TAG, "onRouteSelected: type=" + type + ", info=" + info);
updatePresentation();
}
#Override
public void onRouteUnselected(MediaRouter router, int type, RouteInfo info) {
Log.d(TAG, "onRouteUnselected: type=" + type + ", info=" + info);
updatePresentation();
}
#Override
public void onRoutePresentationDisplayChanged(MediaRouter router, RouteInfo info) {
Log.d(TAG, "onRoutePresentationDisplayChanged: info=" + info);
updatePresentation();
}
};
/**
* Listens for when presentations are dismissed.
*/
private final DialogInterface.OnDismissListener mOnDismissListener =
new DialogInterface.OnDismissListener() {
#Override
public void onDismiss(DialogInterface dialog) {
if (dialog == mPresentation) {
Log.i(TAG, "Presentation was dismissed.");
mPresentation = null;
updateContents();
}
}
};
#SuppressLint({"NewApi"})
public class LauncherSecondScreen extends Presentation
{
public LauncherSecondScreen(Context paramContext, Display paramDisplay)
{
super(paramContext, paramDisplay/*,android.R.style.Theme_Holo_Light_Dialog_NoActionBar*/);
}
protected void onCreate(Bundle paramBundle)
{
super.onCreate(paramBundle);
setContentView(R.layout.dialog_second_screen_content);
//// this.iv_secondScreen_banner = ((ImageView)findViewById(R.id.titleImage));
}
}
}
the app is well, it make one view in the princpale screen and a second view in the second screen , but when i resume the app to background the second screen take the same view of the first screen.
I want to keep the second view showing in the second screen even i resume the app to use another app

Unexpected Crash When trying to open the detailactivity

I am facing a strange problem in my material design app . Some thumbnails are opening and loading details activity as expected , but some are not opening instead there is crash happening . in this video u can see the problem I am facing .
I am attaching the link to my project ZIP file link with this ,My Project
this is the main activity ....
public class MainActivity extends AppCompatActivity implements ReaderAdapter.ReaderOnClickItemHandler {
public final static String READER_DATA = "reader";
public final static String POSITION = "position";
private final static String TAG = MainActivity.class.getSimpleName();
private static final String SAVED_ARRAYLIST = "saved_array_list";
private static final String SAVED_LAYOUT_MANAGER = "layout-manager-state";
private ApiInterface mApiInterface;
private List<Reader> mNetworkDataList;
#BindView(R.id.main_recycler_view)
RecyclerView mRecyclerView;
#BindView(R.id.main_linear_layout)
LinearLayout mErrorLinearLayout;
#BindView(R.id.main_progress_bar)
ProgressBar mProgressBar;
#BindView(R.id.toolbar_main)
Toolbar toolbar;
#BindView(R.id.main_reload_button)
Button mButton;
private ReaderAdapter mReaderAdapter;
private Parcelable onSavedInstanceState = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
if (null != toolbar) {
setSupportActionBar(toolbar);
toolbar.setTitle(getResources().getString(R.string.app_name));
}
mApiInterface = ApiClient.getApiClient().create(ApiInterface.class);
mReaderAdapter = new ReaderAdapter(this, this);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this,
LinearLayoutManager.VERTICAL, false);
mRecyclerView.setAdapter(mReaderAdapter);
mRecyclerView.setLayoutManager(linearLayoutManager);
// getting the data from api using retrofit interface ApiInterface
if (savedInstanceState != null) {
onSavedInstanceState = savedInstanceState.getParcelable(SAVED_LAYOUT_MANAGER);
mNetworkDataList = savedInstanceState.getParcelableArrayList(SAVED_ARRAYLIST);
}
if (null == mNetworkDataList) {
loadData();
mButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
loadData();
}
});
}else {
loadAdapter();
}
}
public void loadData() {
final Call<List<Reader>> listCall = mApiInterface.getAllReaderData();
// now binding the data in the pojo class
listCall.enqueue(new Callback<List<Reader>>() {
//if data is successfully binded from json to the pojo class onResponse is called
#Override
public void onResponse(Call<List<Reader>> call,
Response<List<Reader>> response) {
Log.d(TAG, "Response : " + response.code());
mNetworkDataList = response.body();
loadAdapter();
}
//if data binding is not successful onFailed called
#Override
public void onFailure(Call<List<Reader>> call, Throwable t) {
//cancelling the GET data request
listCall.cancel();
showError();
}
});
}
private void loadAdapter() {
if (null != mNetworkDataList) {
showReaderList();
mReaderAdapter.ifDataChanged(mNetworkDataList);
if (onSavedInstanceState != null) {
mRecyclerView.getLayoutManager().onRestoreInstanceState(onSavedInstanceState);
}
}
}
/**
* this method is for showing the error textview and making all other views gone
*/
private void showError() {
mRecyclerView.setVisibility(View.GONE);
mProgressBar.setVisibility(View.GONE);
mErrorLinearLayout.setVisibility(View.VISIBLE);
}
/**
* this method is for showing the recyclerview and making all other views gone
*/
private void showReaderList() {
mRecyclerView.setVisibility(View.VISIBLE);
mProgressBar.setVisibility(View.GONE);
mErrorLinearLayout.setVisibility(View.GONE);
}
private int numberOfColumns() {
DisplayMetrics displayMetrics = new DisplayMetrics();
this.getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
// You can change this divider to adjust the size of the poster
int widthDivider = 400;
int width = displayMetrics.widthPixels;
int nColumns = width / widthDivider;
if (nColumns < 2) return 2;
return nColumns;
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putParcelable(SAVED_LAYOUT_MANAGER, mRecyclerView.getLayoutManager()
.onSaveInstanceState());
if (mNetworkDataList != null)
outState.putParcelableArrayList(SAVED_ARRAYLIST, new ArrayList<Parcelable>(mNetworkDataList));
}
#Override
public void onClickItem(int position, Reader reader, ImageView mImage, TextView mTitle) {
// Check if we're running on Android 5.0 or higher
Intent readerIntent = new Intent(this, ReaderDetailsActivity.class);
Bundle mBundle = new Bundle();
mBundle.putParcelable(READER_DATA, reader);
mBundle.putInt(POSITION, position);
readerIntent.putExtras(mBundle);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
// Apply activity transition
ActivityOptionsCompat activityOptions = ActivityOptionsCompat.makeSceneTransitionAnimation(
this,
// Now we provide a list of Pair items which contain the view we can transitioning
// from, and the name of the view it is transitioning to, in the launched activity
new Pair<View, String>(mImage,
ReaderDetailsActivity.VIEW_NAME_HEADER_IMAGE),
new Pair<View, String>(mTitle,
ReaderDetailsActivity.VIEW_NAME_HEADER_TITLE));
ActivityCompat.startActivity(this, readerIntent, activityOptions.toBundle());
} else {
// Swap without transition
startActivity(readerIntent);
}
}
}
this is details activity ......
public class ReaderDetailsActivity extends AppCompatActivity {
private static final String TAG = ReaderDetailsActivity.class.getSimpleName();
private static final String SAVED_ARRAYLIST = "saved_array_list";
private static final String SAVED_LAYOUT_MANAGER = "layout-manager-state";
private final static String ARTICLE_SCROLL_POSITION = "article_scroll_position";
// View name of the header image. Used for activity scene transitions
public static final String VIEW_NAME_HEADER_IMAGE = "detail:header:image";
// View name of the header title. Used for activity scene transitions
public static final String VIEW_NAME_HEADER_TITLE = "detail:header:title";
private int position;
private Reader reader;
private int[] scrollPosition = null;
#BindView(R.id.scrollView_details)
ScrollView mScrollView;
#BindView(R.id.details_fragment_title)
TextView mTitle;
#BindView(R.id.imageView_details)
ImageView mImageView;
#BindView(R.id.textView_author_details)
TextView mAuthor;
#BindView(R.id.textView_published_date)
TextView mPublishDate;
#BindView(R.id.textView_description)
TextView mDescription;
#BindView(R.id.floatingActionButton_Up)
FloatingActionButton mFloatingActionButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_reader_details);
ButterKnife.bind(this);
Bundle bundle = getIntent().getExtras();
position=0;
mFloatingActionButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
mScrollView.scrollTo(0,0);
}
});
ViewCompat.setTransitionName(mImageView, VIEW_NAME_HEADER_IMAGE);
ViewCompat.setTransitionName(mTitle, VIEW_NAME_HEADER_TITLE);
if (null != bundle) {
position = bundle.getInt(MainActivity.POSITION);
reader = bundle.getParcelable(MainActivity.READER_DATA);
if(null != reader) {
mTitle.setText(reader.getTitle());
mPublishDate.setText(reader.getPublishedDate());
mAuthor.setText(reader.getAuthor());
GlideApp.with(this)
.load(reader.getPhoto())
.into(mImageView);
mDescription.setText(reader.getBody());
}
}
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
}
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
scrollPosition = savedInstanceState.getIntArray(ARTICLE_SCROLL_POSITION);
if (scrollPosition != null) {
mScrollView.postDelayed(new Runnable() {
public void run() {
mScrollView.scrollTo(scrollPosition[0], scrollPosition[0]);
}
}, 0);
}
}
}
Json link I am parsing for this project .
Here is a screen recording of my project where u can see the problem I am facing , recording
this is a console log when I am trying to debug ....
when it is working fine the console log is 08/09 20:31:31: Launching app
No apk changes detected since last installation, skipping installation of /home/soumyajit/AndroidStudioProjects/MaterialReader/app/build/outputs/apk/debug/app-debug.apk
$ adb shell am force-stop lordsomen.android.com.materialreader
$ adb shell am start -n "lordsomen.android.com.materialreader/lordsomen.android.com.materialreader.activities.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER -D
Connecting to lordsomen.android.com.materialreader
Connected to the target VM, address: 'localhost:8601', transport: 'socket'
and when it is crashing the console log is
08/09 20:31:31: Launching app
No apk changes detected since last installation, skipping installation of /home/soumyajit/AndroidStudioProjects/MaterialReader/app/build/outputs/apk/debug/app-debug.apk
$ adb shell am force-stop lordsomen.android.com.materialreader
$ adb shell am start -n "lordsomen.android.com.materialreader/lordsomen.android.com.materialreader.activities.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER -D
Connecting to lordsomen.android.com.materialreader
Connected to the target VM, address: 'localhost:8601', transport: 'socket'
Disconnected from the target VM, address: 'localhost:8601', transport: 'socket'
thanks in advance ..

Maximum Parcelable size should not be exceed 1mb. In you app it is 2.1 Mb. Without passing app date to the next activity you can try to pass item id and load data in next activity. Otherwise you can cache the list data and you can load the data from the local database in the details activity. If you cannot see crash log in android studio it because it set as "show only selected activity". In this case app get close and then this type of logs doesnot show in the android studio. switch that to No Filter and you can see the all logs.

How to make a slide show with sound with next and previous buttons control

I want to make a slideshow of numbers starting from 0 to 9 in pictures. When i click next button , show the picture of 1 and play sound as 'one' and so on.I want previous button to properly work.. like when I click previous button then go to previous pic and play sound which is related to that pic.
public class Numbers extends Activity {
int i = 1;
private ImageView iv;
Button next;
Button previous;
MediaPlayer ourSong;
private int currentImage = 0;
public int currentAudio = 0;
int[] images = { R.drawable.p1, R.drawable.p2, R.drawable.p3,
R.drawable.p4, R.drawable.p5, R.drawable.p6, R.drawable.p7,
R.drawable.p8, R.drawable.p9, R.drawable.p10};
int[] audios = { R.raw.a1, R.raw.a2, R.raw.a3, R.raw.a4, R.raw.a5,
R.raw.a6, R.raw.a7, R.raw.a8, R.raw.a9, R.raw.a10};
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.nextpre);
iv = (ImageView) findViewById(R.id.ivn);
next = (Button) findViewById(R.id.buttonn);
previous = (Button) findViewById(R.id.buttonp);
// Just set one Click listener for the image
next.setOnClickListener(iButtonChangeImageListener);
previous.setOnClickListener(gButtonChangeImageListener);
}
View.OnClickListener iButtonChangeImageListener = new View.OnClickListener() {
public void onClick(View v) {
try {
// Increase Counter to move to next Image
currentImage++;
currentImage = currentImage % images.length;
iv.setImageResource(images[currentImage]);
ourSong = MediaPlayer.create(Numbers.this,
audios[currentAudio+1]);
ourSong.start();
currentAudio++;
} catch (Exception e) {
}
}
};
View.OnClickListener gButtonChangeImageListener = new View.OnClickListener() {
public void onClick(View v) {
try {
// Decrease Counter to move to previous Image
currentImage--;
currentImage = (currentImage + images.length) % images.length;
iv.setImageResource(images[currentImage]);
MediaPlayer.create(Numbers.this, audios[currentAudio]);
ourSong.start();
currentAudio--;
} catch (Exception e) {
}
}
};
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
ourSong.release();
finish();
}
#Override
protected void onStart() {
super.onStart();
ourSong = MediaPlayer.create(Numbers.this,
audios[0]);
ourSong.start();
}
}

Hmm if you're trying to make a slide show, you might want to look into view pagers they look like this:
View pagers are highly customizable, You can add buttons and images and pretty much almost anything a fragment can hold on each screen. Not sure what your skill level is but ill tell you whats involved in getting this to work.
Create a layout with a view pager in it.
Create a class that extends the FragmentPagerAdapter
Override getItem() method in the adapter (this is where you define your different "screens"
Create a class that extends fragment for each screen you want to show your users.
Doing it this way in order to switch screens u just have to call setCurrentItem to change pages (when user clicks next or prev)
--edit--
Apparently theres also a something called an ImageSwitcher.
They look like this:
This is actually better for your case since you only want images. It looks a lot easier to implement than a view pager. This describes how to implement it: http://www.tutorialspoint.com/android/android_imageswitcher.htm