Change custom button size for layouts and containe

问题:

I have a custom class (touchbutton) extending the TextView class. I am having trouble resizing the button manually. I can get the button to work for only one type of layout or container, but not both. For the most part, Touchbutton is in gridviews so my method to change the size is as so:

private void setLayout(buttonsize_t size) {

    log("Setting Layout: "+buttonsize_t.getPxl(size));

    final float scale = getContext().getResources().getDisplayMetrics().density;
    int dim = (int) (buttonsize_t.getPxl(size) * scale + 0.5f);

    AbsListView.LayoutParams params = (AbsListView.LayoutParams) getLayoutParams();
    if (params != null) {
        params.height = dim;
        params.width = dim;
    }
    else {
        params = new AbsListView.LayoutParams(dim,dim);
    }
    setLayoutParams(params);
}

However, when the TouchButton is resized in a LinearLayout (for example) I get a crash with the Logcat:

09-01 19:18:35.630: ERROR/AndroidRuntime(20793): java.lang.ClassCastException: android.widget.LinearLayout$LayoutParams cannot be cast to android.widget.AbsListView$LayoutParams
09-01 19:18:35.630: ERROR/AndroidRuntime(20793):     at com.ians.aac3.TouchButton.setLayout(TouchButton.java:204)

Line 204 refers to the instantiation of params.

I noticed that both GridView and LinearLayout share the parent ViewGroup, so i tried using ViewGroup.LayoutParams. This, however, this will lead to the same behavior for gridviews (logcat citing the same line).

Does anyone know how I might make this work for any type of layout or widget?

UPDATE: As recommended i tried with View group again:

import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.util.Log;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.widget.TextView;
.....
ViewGroup.LayoutParams params = getLayoutParams();
        if (params != null) {
            params.height = dim;
            params.width = dim;
        }
        else {
            params = new LayoutParams(dim,dim);
        }
        setLayoutParams(params);

or without trying to recycle the current layoutparams:

setLayoutParams(new ViewGroup.LayoutParams(dim, dim));

And i get the same type of error:

09-02 09:10:49.680: ERROR/AndroidRuntime(7069): java.lang.ClassCastException: android.view.ViewGroup$LayoutParams cannot be cast to android.widget.AbsListView$LayoutParams
09-02 09:10:49.680: ERROR/AndroidRuntime(7069):     at android.widget.GridView.onMeasure(GridView.java:1028)
09-02 09:10:49.680: ERROR/AndroidRuntime(7069):     at android.view.View.measure(View.java:10828)
09-02 09:10:49.680: ERROR/AndroidRuntime(7069):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4351)
09-02 09:10:49.680: ERROR/AndroidRuntime(7069):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:267)
09-02 09:10:49.680: ERROR/AndroidRuntime(7069):     at android.view.View.measure(View.java:10828)
09-02 09:10:49.680: ERROR/AndroidRuntime(7069):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4351)
09-02 09:10:49.680: ERROR/AndroidRuntime(7069):     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1284)

Update 2: It seems that using the ViewGroup.LayoutParams specified above works for the LinearLayout. However, as seen above, the gridview doesn't like it...

回答1:

To understand what happens here you need to look in the Android source. There is a method in ViewGroup generateLayoutParams which JavaDoc states:

Returns a safe set of layout parameters based on the supplied layout params. When a ViewGroup is passed a View whose layout params do not pass the test of checkLayoutParams(android.view.ViewGroup.LayoutParams), this method is invoked. This method should return a new set of layout params suitable for this ViewGroup, possibly by copying the appropriate attributes from the specified set of layout params.

If you look at LinearLayout and AbsListView (the parent of GridView) source you'll see they convert their children layout params to LinearsLayout.LayoutParams and AbsListView.LayoutParams respectively. But this conversion only happens when the child is added to the layout.
Thus if you add your TouchButton to the LinearLayout (programmaticaly or via XML) it will receive LinearsLayout.LayoutParams and, if you add it to the GridView (via an adapter) it receives AbsListView.LayoutParams.
But if you set layout params manually afterwards, you will get ClassCastException somewhere in the parent container code (since it expects its children layout params to be of some specific type).

For the solution of your issue I suggest you the following:

private void setLayout(buttonsize_t size) {

    log("Setting Layout: "+buttonsize_t.getPxl(size));

    final float scale = getContext().getResources().getDisplayMetrics().density;
    int dim = (int) (buttonsize_t.getPxl(size) * scale + 0.5f);

    ViewGroup.LayoutParams params = (ViewGroup.LayoutParams) getLayoutParams();
    if (params != null) {  
        params.height = dim;
        params.width = dim;
        setLayoutParams(params);
    } else {
      // the LayoutParams was not set yet, it must be the GridView 
      // which delays setting till child rendering
      params = new AbsListView.LayoutParams(dim, dim);
      setLayoutParams(params);
    }
}

回答2:

Why are you casting LayoutParams at all?

Button.getLayoutParams() should return ViewGroup.LayoutParams, which you can access the height and width on - no cast needed. Are you sure when you tried ViewGroup.LayoutParams you didn't do something like:

ViewGroup.LayoutParams params = (AbsListView.LayoutParams) getLayoutParams();

(That'll still fail).

In any case, use this:

ViewGroup.LayoutParams params = getLayoutParams();

Then if you still get an exception, post that one - not the one with the casting.