Refer to the code below:
public class ExpandableTextView extends TextView {
public ExpandableTextView(Context context) {
this(context, null, null);
}
public ExpandableTextView(Context context, AttributeSet attrs) {
this(context, attrs, null);
}
public ExpandableTextView(Context context, AttributeSet attrs, Runnable runnable) {
super(context, attrs);
TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.ExpandableTextView);
this.trimLength = typedArray.getInt(R.styleable.ExpandableTextView_trimLength, DEFAULT_TRIM_LENGTH);
typedArray.recycle();
setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
trim = !trim;
setText();
requestFocusFromTouch();
}
});
}
public ExpandableTextView(Context context, AttributeSet attrs, Activity activity) {
super(context, attrs);
TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.ExpandableTextView);
this.trimLength = typedArray.getInt(R.styleable.ExpandableTextView_trimLength, DEFAULT_TRIM_LENGTH);
typedArray.recycle();
setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
trim = !trim;
setText();
requestFocusFromTouch();
}
});
}
}
method like this(context, null, null); could refer to two other constructor methods, is there any way that i can specify which one it refers to rather than changing the signature or the "null"?
thanks
Sure, just cast the null into the signature type!
new ExpandableTextView(context, (AttributeSet)null, (Runnable)null)
Your code should not work as Compiler will throw error mentioning ambiguous method. Because Java will always try to use the most specific applicable version of a method that's available (see JLS ยง15.12.2). And null is a valid value for the types Context, AttributeSet and Runnable. Therefore all 3 version are applicable.
Related
I have extended the Button class and I want to run methods like isInternetConnected and isUserLoggedIn when user click to this button and after perform onclick if all condition satisfied.
For Example if I created simple form where user name, email, phone no. and Submit Button placed. When user click on submit first it checks isInternetConnected and isUserLoggedIn if this satisfies then perform final operation saves user data to server or anywhere.
public class CustomButton extends Button {
private static final String TAG = "CustomButton";
public CustomButton(Context context) {
super(context);
}
public CustomButton(Context context, AttributeSet attrs) {
super(context, attrs);
}
public CustomButton(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
public CustomButton(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
}
If this is possible then I don't need to check every time
`mButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (!isInternetConnected) {
//show dialog or snackbar
} else if (!isUserLoggedIn) {
//show dialog or snackbar
}else {
// save data
}
}
});`
Now i understand what you are asking. Ideal solution for your problem would be AOP (aspect oriented programming).
These should help you:
https://medium.com/#jdvp/aspect-oriented-programming-in-android-159054d52757
https://fernandocejas.com/2014/08/03/aspect-oriented-programming-in-android/
This lib should help you:
https://www.eclipse.org/aspectj/
This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 4 years ago.
I'm initialing imageview at DailyCardView.java which are called by a fragment. But it keeps showing nullPointerException. I really don't know where went wrong... Guys help me><
I tried getRootView() to get view of Fragment so i can code:iv=(ImageView)getRootView().findViewById(R.id.iv);
But it still not work.
**//Fragment**
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.home_fragment, container, false);
dailyStackLayout = (DailyStackLayout)view.findViewById(R.id.dailyStackLayout);
dailyStackLayout.setDatas(dailyFoodList);
return view;
}
**//DailyStackLayout**
public DailyStackLayout(Context context) {
this(context, null);
}
public DailyStackLayout(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public DailyStackLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
public void init() {
params = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
scaleY = DensityUtil.dip2px(getContext(), BASESCALE_Y_VALUE);
}
public void setDatas(List<DailyFood> dailyFoodList) {
this.dailyFoodList = dailyFoodList;
if (dailyFoodList == null) {
return;
}
for (int i = index; index < i + STACK_SIZE; index++) {
dc = new DailyCardView(getContext());
dc.bind(dailyFoodList.get(index));
}
}
**//DailyCardView**
public DailyCardView(Context context) {
super(context, null);
}
public DailyCardView(Context context, AttributeSet attrs) {
this(context, attrs,0);
}
public DailyCardView(Context context, AttributeSet attrs, int defStyleAttr)
{
super(context, attrs, defStyleAttr);
init(context);
}
public void init(Context context) {
if (!isInEditMode()) {
inflate(context, R.layout.item_daily_card, this);
iv = (ImageView)findViewById(R.id.iv);
}
}
public void bind(DailyFood dailyFood) {
if (dailyFood == null) {return;}
if (!TextUtils.isEmpty(dailyFood.getId())) {
Glide.with(**iv.getContext()**) // **NullPointerException**!
.load(Constant.Daily_URL+dailyFood.getId()+".jpg")
.into(iv);
}
I expect to load the image right but it went wrong at getContext().
dc = new DailyCardView(getContext());
This calls the DailyCardView(Context) constructor that does not call init():
public DailyCardView(Context context) {
super(context, null);
}
The init() call would init iv. And then you call bind() that assumes that iv is initialised. Bang, NPE.
Either change the super in the constructor to this to delegate to another constructor that calls init(), or just add a call to init().
SO here's the situation. I am extending a class in Java and I Need to provide 3 constructors with 1, 2 and 3 parameters respectively.
public class MessageButton extends ImageButton {
private String number;
public MessageButton(Context context) {
super(context);
}
public MessageButton(Context context, AttributeSet attrs) {
super(context, attrs);
if( attrs.getAttributeValue("uk.co.gsteinert.ssbb", "number") != null ) {
this.number = attrs.getAttributeValue("uk.co.gsteinert.ssbb", "number");
}
}
public MessageButton(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
if( attrs.getAttributeValue("uk.co.gsteinert.ssbb", "number") != null ) {
this.number = attrs.getAttributeValue("uk.co.gsteinert.ssbb", "number");
}
}
}
Obviously there's a bit of duplication there (in the last two constructors) and I want to reduce this.
I see two options:
Move the code into a setup() function, and call that from each constructor. This reduces the duplicated code, but still requires the call in each constructor.
Use this() in all but the last constructor. The only issue is that the defaults for the optional parameters are not null. I would need to check the source of the superclass to work out what values to use.
SO the way I see it, either way I have to duplicate code (the function call) or make assumptions about the superclass (the default values). I know both of these are less than desirable but which is the greater evil?
Or am I missing something?
Thanks
As you mentioned, I would use this() for all your constructors and check which default values are used in the parent class and supply those instead of null (used in this example). You are using this class for your custom code, so you should know what values you want as default.
public class MessageButton extends ImageButton {
private String number;
public MessageButton(Context context) {
this(context, null);
}
public MessageButton(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public MessageButton(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
if (attrs.getAttributeValue("uk.co.gsteinert.ssbb", "number") != null) {
this.number = attrs.getAttributeValue("uk.co.gsteinert.ssbb", "number");
}
}
}
You can call one constructor from another (without creating a new instance) with this
public MyClass(String value) {
....
}
public MyClass() {
this(defaultValue);
}
public class MessageButton extends ImageButton {
private String number;
public MessageButton(Context context) {
this(context,null,0);
}
public MessageButton(Context context, AttributeSet attrs) {
this(context, attrs,0);
}
public MessageButton(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
if(attrs!=null){
if( attrs.getAttributeValue("uk.co.gsteinert.ssbb", "number") != null ) {
this.number = attrs.getAttributeValue("uk.co.gsteinert.ssbb", "number");
}
}}
}
I have a custom spinner
I have a Hint label that is in the last position of my array(spinner), so to display it I set selection to the last position, like this:
ArrayAdapter myAdapter = new MySpinnerAdapter(this,R.layout.spinner_item,createMyList());
myAdapter.setDropDownViewResource(spinner_item);
mySpinner.setAdapter(subCategoryAdapter);
mySpinner.setSelection(myList.size() - 1);
It's working perfectly, but when I touch on Spinner to select a item, the scroll it's "focusing" the bottom of spinner, because of my setSelection.
How can I focus on the first item of the spinner OR "scroll" to the top of it?
Thanks!
You can achieve this by extending Spinner and overriding methods that are responsible for setup and showing the list of values in the drop down:
public class CustomSpinner extends Spinner {
private boolean mToggleFlag = true;
public CustomSpinner(Context context, AttributeSet attrs, int defStyle, int mode) {
super(context, attrs, defStyle, mode);
}
public CustomSpinner(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public CustomSpinner(Context context, AttributeSet attrs) {
super(context, attrs);
}
public CustomSpinner(Context context, int mode) {
super(context, mode);
}
public CustomSpinner(Context context) {
super(context);
}
#Override
public int getSelectedItemPosition() {
if (!mToggleFlag) {
return 0; // Gets to the first element
}
return super.getSelectedItemPosition();
}
#Override
public boolean performClick() {
mToggleFlag = false;
boolean result = super.performClick();
mToggleFlag = true;
return result;
}
}
I have a GridView which I am constantly adding views to. When the view adds to the grid I wish for it to do an animation. However, as I have to use setAdapter() to refresh the GridView, it ends up animating all views, as they are all being re-added. Is there anyway around this?
Here is the code for my view I am adding:
public class GridImageView extends ImageView {
public GridImageView(Context context) {
super(context);
}
public GridImageView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public GridImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
#Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
ScaleAnimation anim = new ScaleAnimation(0,1,0,1);
anim.setDuration(1000);
anim.setFillAfter(true);
this.startAnimation(anim);
}
}
As always, thanks for your help
Thanks to Luksprog's suggestion, I have set a flag in my custom view which will determine if the view should animate when added to the Grid View.
public class GridImageView extends ImageView
{
private boolean _animate = false;
public GridImageView(Context context) {
super(context);
}
public GridImageView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public GridImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
#Override
protected void onAttachedToWindow() {
if(_animate){
super.onAttachedToWindow();
ScaleAnimation anim = new ScaleAnimation(0,1,0,1);
anim.setDuration(1000);
anim.setFillAfter(true);
this.startAnimation(anim);
}
}
public void set_animate(boolean _animate) {
this._animate = _animate;
}
}
and my adapter in its GetView() function checks if it is the last in the array list, and sets the flag to true if so.
if( i == ( _gridDetailsArrayList.size() - 1 ))
holder.gridImage.set_animate(true);