一旦高度为0,LinearyLayout将不会调整大小

Question

有一个奇怪的.我已经把它归结为一个非常简单的例子.真的想不出来.

我在LinearLayout中有一个LinearLayout.我想使用动画来调整孩子的大小(有时我会做一些治疗).这是我的布局XML.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent" android:layout_height="fill_parent"
    android:orientation="vertical" >

    <LinearLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:orientation="vertical">
        <!-- Lots more controls will appear above -->
        <LinearLayout android:layout_width="fill_parent" android:layout_height="0dp" android:id="@+id/animation_subject">
            <TextView
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:text="@string/hello"
                android:gravity="center" />
        </LinearLayout> 
        <!-- Lots more controls will appear below -->
    </LinearLayout>

    <Button android:text="Slide it Down!" android:layout_width="fill_parent" android:layout_height="wrap_content" android:onClick="btnDoAnimDown_OnClick" />

</LinearLayout>

现在,正如您所看到的,有一个按钮,这是该按钮的代码.

public void btnDoAnimDown_OnClick(View v)
{
    View pnlSlider = findViewById(R.id.animation_subject);
    pnlSlider.measure(1000, 1000);
    DropDownAnim anim = new DropDownAnim(pnlSlider, pnlSlider.getMeasuredHeight(), true);
    anim.setDuration(2000);
    pnlSlider.startAnimation(anim);

    return;     
}

如果你现在运行它,它不会下滑.完全没有.但是,如果您要将Button移动到我已命名为Overview的LinearLayout并将其放在Child LinearLayout之后,那么它就可以了!像这样...

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent" android:layout_height="fill_parent"
    android:orientation="vertical" >

    <LinearLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:orientation="vertical">
        <!-- Lots more controls will appear above -->
        <LinearLayout android:layout_width="fill_parent" android:layout_height="0dp" android:id="@+id/animation_subject">
            <TextView
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:text="@string/hello"
                android:gravity="center" />
        </LinearLayout> 
        <!-- Lots more controls will appear below -->
        <Button android:text="Slide it Down!" android:layout_width="fill_parent" android:layout_height="wrap_content" android:onClick="btnDoAnimDown_OnClick" />
    </LinearLayout>

</LinearLayout>

现在它正如预期的那样向下滑动.很明显,父布局会有一些东西......当getMeasuredHeight()返回正确的值时,它只是动画实际上没有运行!

这是动画类,我错过了一些傻事吗？可能是我!

import android.util.Log;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.Transformation;

public class DropDownAnim extends Animation {
    int targetHeight;
    View view;
    boolean down;

    public DropDownAnim(View view, int targetHeight, boolean down) {
        this.view = view;
        this.targetHeight = targetHeight;
        this.down = down;
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        int newHeight;
        if (down) {
            newHeight = (int) (targetHeight * interpolatedTime);
        } else {
            newHeight = (int) (targetHeight * (1 - interpolatedTime));
        }
        Log.d("new height", String.valueOf(newHeight));
        view.getLayoutParams().height = newHeight;
        view.requestLayout();
    }

    @Override
    public void initialize(int width, int height, int parentWidth,
            int parentHeight) {
        super.initialize(width, height, ((View)view.getParent()).getWidth(), parentHeight);
    }

    @Override
    public boolean willChangeBounds() {
        return true;
    }
}

任何帮助都会很棒!

Answer 1

我不知道为什么你的代码不想做动画。但我做了一点改变就解决了。我所做的是将动画应用于父布局，而不是您正在转换的布局。这是xml的代码，我只向父布局添加了一个Id：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent" android:layout_height="fill_parent"
    android:orientation="vertical" >

    <LinearLayout android:id="@+id/animation_subject_parent" android:layout_width="fill_parent" android:layout_height="wrap_content" android:orientation="vertical">
        <!-- Lots more controls will appear above -->
        <LinearLayout android:layout_width="fill_parent" android:layout_height="0dp" android:id="@+id/animation_subject">
            <TextView
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:text="@string/hello"
                android:gravity="center" />
        </LinearLayout> 
        <!-- Lots more controls will appear below -->
    </LinearLayout>
        <Button android:text="Slide it Down!" android:layout_width="fill_parent" android:layout_height="wrap_content" android:onClick="btnDoAnimDown_OnClick" />

</LinearLayout>

这是按钮 CLI 的代码：

public void btnDoAnimDown_OnClick(View v)
{
    View pnlSlider = findViewById(R.id.animation_subject);
    View parent = findViewById(R.id.animation_subject_parent);

    pnlSlider.measure(1000, 1000);
    DropDownAnim anim = new DropDownAnim(pnlSlider, pnlSlider.getMeasuredHeight(), true);
    anim.setDuration(2000);

    parent.startAnimation(anim);

    return;     
}