图片放大缩小

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
android:id="@+id/relativeLayout"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center_horizontal"
xmlns:android="http://schemas.android.com/apk/res/android">

<ImageView android:id="@+id/imageView"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center">
</ImageView>

<LinearLayout
android:id="@+id/linearLayout"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true">

<Button android:id="@+id/bt_smaller"
android:layout_width="100px"
android:layout_height="50px"
android:text="缩小" >
</Button>

<Button android:id="@+id/bt_bigger"
android:layout_width="100px"
android:layout_height="50px"
android:text="放大" >
</Button>

</LinearLayout>
</RelativeLayout>

package sunny.test;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

import android.R.integer;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Camera;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.Toast;
import android.widget.ImageView.ScaleType;
import android.widget.LinearLayout;
import android.widget.LinearLayout.LayoutParams;
import android.widget.SimpleAdapter.ViewBinder;
import android.widget.ProgressBar;
import android.widget.ViewFlipper;

public class MainActivity extends Activity {
private ImageView imageView;
private Button bt_bigger;
private Button bt_smaller;
private RelativeLayout layout; //容器
private Bitmap bmp; //bitmap图片对象
private int primaryWidth; //原图片宽
private int primaryHeight; //原图片高
private double scaleWidth, scaleHeight; //高宽比例

public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

getWidget();
}

/**
* 获取控件对象并初始化
*/
private void getWidget() {
imageView = (ImageView)findViewById(R.id.imageView); // img
layout = (RelativeLayout)findViewById(R.id.relativeLayout); //layout
bt_bigger = (Button)findViewById(R.id.bt_bigger); //button
bt_smaller = (Button)findViewById(R.id.bt_smaller); //button

//创建BitMap对象，用于显示图片
bmp = BitmapFactory.decodeResource(this.getResources(), R.drawable.zhou1);
//原始大小
primaryWidth = bmp.getWidth();
primaryHeight = bmp.getHeight();
//初始比例为1
scaleWidth = scaleHeight = 1;

imageView.setImageBitmap(bmp);

bt_bigger.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
scale(1.25, 1.25);
}
});

bt_smaller.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
scale(0.8, 0.8);
}
});

}

/**
* 缩放
*/
private void scale(double scale_width, double scale_height) {
//这种方法，有点不好是：如果图片大小超出屏幕会报错。
if((scale_width > 1 && scaleWidth * primaryWidth >= getWindowManager().getDefaultDisplay().getWidth())
|| (scale_width > 1 && scale_height * primaryHeight >= getWindowManager().getDefaultDisplay().getHeight())){
bt_bigger.setEnabled(false);
}else {
bt_bigger.setEnabled(true);
}
scaleWidth = scaleWidth * scale_width; //缩放到原来的*倍
scaleHeight = scaleHeight * scale_height;

Matrix matrix = new Matrix(); //矩阵，用于图片比例缩放
matrix.postScale((float)scaleWidth, (float)scaleHeight); //设置高宽比例（三维矩阵）

//缩放后的BitMap
Bitmap newBmp = Bitmap.createBitmap(bmp, 0, 0, primaryWidth, primaryHeight, matrix, true);

//重新设置BitMap
imageView.setImageBitmap(newBmp);
}
}

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