以動畫的方式實現View的展開和縮放

<pre name="code" class="java"><span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);"><span style="font-size:18px;">Activity代碼如下</span></span>

<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);"><span style="font-size:18px;">
</span></span>

<span style="font-size:18px;">import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.AnimatorSet;
import android.animation.ObjectAnimator;
import android.animation.ValueAnimator;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.view.animation.AccelerateInterpolator;
import android.widget.Button;
import android.widget.LinearLayout;

public class MainActivity extends AppCompatActivity {
    private LinearLayout contentPanel;
    private Button expand_btn;
    private int height;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        contentPanel= (LinearLayout) findViewById(R.id.contentPanel);
        expand_btn= (Button) findViewById(R.id.expand_btn);
        contentPanel.measure(0, 0);
        height=contentPanel.getMeasuredHeight();

    }
    public void to(View v){
        if(contentPanel.isShown()){
            contraction();
        }else{
            expand();
        }
    }

    /**
     * 收縮
     */
    private void contraction(){
        AnimatorSet set=new AnimatorSet();
        //根據值的改變，動態設置view的高度
        ValueAnimator valueAnimator=ValueAnimator.ofInt(height,0);
        valueAnimator.setDuration(1000);
        valueAnimator.setInterpolator(new AccelerateInterpolator());

        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                int height = (int) animation.getAnimatedValue();
                Log.e("height", height + "");
                LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, height);
                contentPanel.setLayoutParams(params);
            }
        });
        valueAnimator.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                contentPanel.setVisibility(View.GONE);
                expand_btn.setText("展開");
            }
        });
        //將view從不透明變成透明
        ObjectAnimator alpha=ObjectAnimator.ofFloat(contentPanel,"alpha",1f,0f);
        alpha.setDuration(1000);

        set.play(valueAnimator).with(alpha);
        set.start();
    }

    /**
     * 展開
     */
    private void expand(){
        contentPanel.setVisibility(View.VISIBLE);

        AnimatorSet set=new AnimatorSet();

        ValueAnimator valueAnimator=ValueAnimator.ofInt(0,height);
        valueAnimator.setDuration(1000);
        valueAnimator.setInterpolator(new AccelerateInterpolator());
        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                int height = (int) animation.getAnimatedValue();
                Log.e("height", height + "");
                LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, height);
                contentPanel.setLayoutParams(params);
            }
        });
        valueAnimator.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                expand_btn.setText("收起");
            }
        });
        //將view從透明變成不透明
        ObjectAnimator alpha=ObjectAnimator.ofFloat(contentPanel,"alpha",0f,1f);
        alpha.setDuration(1000);

        set.play(valueAnimator).with(alpha);
        set.start();
    }
}
</span></span>

XML代碼：

<span style="font-family: Arial, Helvetica, sans-serif;"><span style="font-size:18px;"><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"</span></span>

<span style="font-size:18px;">    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <Button
        android:id="@+id/expand_btn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="to"
        android:text="展開"/>
    <LinearLayout
        android:id="@+id/contentPanel"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="11111111111111111111111111111111111111"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="11111111111111111111111111111111111111"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="11111111111111111111111111111111111111"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="11111111111111111111111111111111111111"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="11111111111111111111111111111111111111"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="11111111111111111111111111111111111111"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="11111111111111111111111111111111111111"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="11111111111111111111111111111111111111"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="11111111111111111111111111111111111111"/>
    </LinearLayout>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text=""/>
</LinearLayout>
</span></span>