Android中属性动画Property Animation使用示例(四)

MainActivity如下:

package cc.cn;

import android.animation.AnimatorInflater;
import android.animation.IntEvaluator;
import android.animation.ObjectAnimator;
import android.animation.ValueAnimator;
import android.animation.ValueAnimator.AnimatorUpdateListener;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
/**
 * Demo描述:
 * 利用属性动画将Button变宽的四种方式示例
 *
 * 参考资料:
 * 1 http://blog.csdn.net/singwhatiwanna/article/details/17841165
 * 2 关于属性动画的中文文档,请参见:
 *   http://blog.csdn.net/think_soft/article/details/7703684
 *   http://wiki.eoeandroid.com/Property_Animation
 *   Thank you very much
 *
 */
public class MainActivity extends Activity {
	private Button mScaleXFirstButton;
	private Button mScaleXSecondButton;
	private Button mScaleXThirdButton;
	private Button mScaleXFourthButton;
	private ObjectAnimator mObjectAnimator1;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        init();
    }

    private void init(){

    	//------>以下为利用属性动画将Button变宽的方式一
    	//该方式存在的问题:Button被拉伸的同时按钮中的文字亦被拉伸,效果不好.
    	//解决方法:参见以下的方式二、三和四
    	mScaleXFirstButton=(Button) findViewById(R.id.scaleXFirstButton);
    	mScaleXFirstButton.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				mObjectAnimator1.start();
			}
		});
    	mObjectAnimator1=(ObjectAnimator)AnimatorInflater.loadAnimator(this, R.animator.scalexanimator);
    	mObjectAnimator1.setTarget(mScaleXFirstButton);

    	//------>以下为利用属性动画将Button变宽的方式二
    	//该方式中可将Button变宽.
        //但是存在一个问题:
    	//布局文件中scaleXSecondButton宽度的设置是android:layout_width="wrap_content"
    	//若将宽度改为一个具体的值比如250dip,那么此时是没有动画效果的.
    	//解决办法参见方式三
    	mScaleXSecondButton=(Button) findViewById(R.id.scaleXSecondButton);
    	mScaleXSecondButton.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				ObjectAnimator.ofInt(mScaleXSecondButton, "width", 500).setDuration(2000).start();
			}
		});

    	//------>以下为利用属性动画将Button变宽的方式三
    	//该方法解决了在方式二中的问题.
    	//原因分析:
    	//属性动画要求动画作用的对象提供该属性的get和set方法.即在此例中
    	//我们要修改的是对象的width属性.所以要有该属性对应的get和set方法
    	mScaleXThirdButton=(Button) findViewById(R.id.scaleXThirdButton);
    	final ViewWrapper viewWrapper=new ViewWrapper(mScaleXThirdButton);
    	mScaleXThirdButton.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				 ObjectAnimator.ofInt(viewWrapper, "width", 500).setDuration(2000).start();
			}
		});

    	//------>以下为利用属性动画将Button变宽的方式四
    	//在该示例中主要采用了ValueAnimator
    	mScaleXFourthButton=(Button) findViewById(R.id.scaleXFourthButton);
    	mScaleXFourthButton.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				startPropertyAnimation(mScaleXFourthButton,mScaleXFourthButton.getWidth(),500);
			}
		});
    }

    private void startPropertyAnimation(final View target, final int startValue, final int endValue){
    	final IntEvaluator intEvaluator=new IntEvaluator();
    	//将动画值限定在(1,100)之间
		ValueAnimator valueAnimator=ValueAnimator.ofInt(1,100);
		//动画持续时间
		valueAnimator.setDuration(5000);
		//监听动画的执行
		valueAnimator.addUpdateListener(new AnimatorUpdateListener() {
			@Override
			public void onAnimationUpdate(ValueAnimator valueAnimator) {
				//得到当前瞬时的动画值,在(1,100)之间
				Integer currentAnimatedValue=(Integer) valueAnimator.getAnimatedValue();
				//计算得到当前系数fraction
				float fraction=currentAnimatedValue/100f;
				System.out.println("currentAnimatedValue="+currentAnimatedValue+",fraction="+fraction);
				//评估出当前的宽度其设置
				target.getLayoutParams().width=intEvaluator.evaluate(fraction, startValue, endValue);
				target.requestLayout();
			}
		});
		//开始动画
		valueAnimator.start();
	}

	private class ViewWrapper {

		private View mTargetView;

		public ViewWrapper(View target) {
			mTargetView = target;
		}

		public int getWidth() {
			return mTargetView.getLayoutParams().width;
		}

		public void setWidth(int width) {
			mTargetView.getLayoutParams().width = width;
			mTargetView.requestLayout();
		}
	}

}

main.xml如下:

<?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" >
 <Button
        android:id="@+id/scaleXFirstButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="100dip"
        android:text="scaleXFirstButton" />

   <Button
        android:id="@+id/scaleXSecondButton"
        android:layout_width="wrap_content"
        android:layout_marginLeft="100dip"
        android:layout_height="wrap_content"
        android:text="scaleXSecondButton" />

   <Button
        android:id="@+id/scaleXThirdButton"
        android:layout_width="250dip"
        android:layout_marginLeft="100dip"
        android:layout_height="wrap_content"
        android:text="scaleXThirdButton" />

   <Button
        android:id="@+id/scaleXFourthButton"
        android:layout_width="250dip"
        android:layout_marginLeft="100dip"
        android:layout_height="wrap_content"
        android:text="scaleXFourthButton" />

</LinearLayout>

scalexanimator.xml如下:

<?xml version="1.0" encoding="utf-8"?>
<objectAnimator
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:propertyName="scaleX"
    android:duration="3000"
    android:valueFrom="1.0"
    android:valueTo="2.0"
    android:repeatCount="1"
    android:repeatMode="reverse"
     >
</objectAnimator>