在android中，图片的放大和缩小是很重要的一个方法，我们主要用到的就是bitmap、MotionEvent
、Matrix、KeyEvent、OnTouchListene、ImageView。还有很多，在做图片的放大和缩小我们要知道的是， 取得屏幕分辨率大小，始化相关变量，还要定义的是图片缩小和放大的比例，我们还得判断图片太大，超出屏幕怎么办。下面我们就来看看图片的放大和缩小吧。

package EOE.android; import Android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.graphics.Matrix;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.GestureDetector;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;
import android.view.GestureDetector.OnGestureListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.Toast; public class DisplayImage extends Activity implements OnTouchListener, OnGestureListener {
private static final String TAG = "DisplayImage";
private static final int FLING_MIN_DISTANCE = 100;
private static final int FLING_MIN_VELOCITY = 200; /* 相关变量声明 */
private ImageView mImageView;
private Button mButton01;
private Button mButton02;
private FrameLayout layout1;
private LinearLayout layoutImage;
private Bitmap bmp;
private int id=0;
private int displayWidth;
private int displayHeight;
private float scaleWidth=1;
private float scaleHeight=1;
private GestureDetector mGestureDetector; /** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
/* 加载display.xml Layout */
setContentView(R.layout.display); /* 取得屏幕分辨率大小 */
DisplayMetrics dm=new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(dm);
displayWidth=dm.widthPixels;
displayHeight=dm.heightPixels; /* 初始化相关变量 */
Bundle bundle = this.getIntent().getExtras();
Integer imageId = bundle.getInt("imageId");
Log.i(TAG, "onCreate, imageId = " + imageId); bmp=BitmapFactory.decodeResource(getResources(), imageId);
mImageView = (ImageView)findViewById(R.id.myImageView);
mImageView.setImageBitmap(bmp);
mImageView.setOnTouchListener(this);
mImageView.setLongClickable(true); layout1 = (FrameLayout)findViewById(R.id.layout1);
layoutImage = (LinearLayout)findViewById(R.id.layoutImage);
mButton01 = (Button)findViewById(R.id.myButton1);
mButton02 = (Button)findViewById(R.id.myButton2); /* 缩小按钮onClickListener */
mButton01.setOnClickListener(new Button.OnClickListener() {
@Override
public void onClick(View v) {
small();
}
}); /* 放大按钮onClickListener */
mButton02.setOnClickListener(new Button.OnClickListener() {
@Override
public void onClick(View v) {
big();
}
});
} // 用户轻触触摸屏，由1个MotionEvent ACTION_DOWN触发
@Override
public boolean onDown(MotionEvent e) {
// TODO Auto-generated method stub
// Toast.makeText(this, "onDown", Toast.LENGTH_SHORT).show();
Log.i(TAG, "onDown..."); return false;
} /* 用户按下触摸屏、快速移动后松开，由1个MotionEvent ACTION_DOWN,
* 多个ACTION_MOVE, 1个ACTION_UP触发
* 参数解释：
* e1：第1个ACTION_DOWN MotionEvent
* e2：最后一个ACTION_MOVE MotionEvent
* velocityX：X轴上的移动速度，像素/秒
* velocityY：Y轴上的移动速度，像素/秒
* 触发条件 ：
* X轴的坐标位移大于FLING_MIN_DISTANCE，且移动速度大于FLING_MIN_VELOCITY个像素/秒
* @see android.view.GestureDetector$OnGestureListener#onFling(android.view.MotionEvent, android.view.MotionEvent, float, float)
*/
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
float velocityY) {
// TODO Auto-generated method stub
Log.i(TAG, "onFling..."); if (e1.getX() - e2.getX() > FLING_MIN_DISTANCE
&& Math.abs(velocityX) > FLING_MIN_VELOCITY) {
// Fling left Toast.makeText(this, "Fling Left", Toast.LENGTH_SHORT).show();
} else if (e2.getX() - e1.getX() > FLING_MIN_DISTANCE
&& Math.abs(velocityX) > FLING_MIN_VELOCITY) { // Fling right Toast.makeText(this, "Fling Right", Toast.LENGTH_SHORT).show();
} return false;
} // 用户长按触摸屏，由多个MotionEvent ACTION_DOWN触发
@Override
public void onLongPress(MotionEvent e) {
// TODO Auto-generated method stub
Log.i(TAG, "onLongPress..."); } // 用户按下触摸屏，并拖动，由1个MotionEvent ACTION_DOWN, 多个ACTION_MOVE触发
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,
float distanceY) {
// TODO Auto-generated method stub
Log.i(TAG, "onScroll..."); return false;
} // 用户轻触触摸屏，尚未松开或拖动，由一个1个MotionEvent ACTION_DOWN触发
// 注意和onDown()的区别，强调的是没有松开或者拖动的状态
@Override
public void onShowPress(MotionEvent e) {
// TODO Auto-generated method stub
Log.i(TAG, "onShowPress..."); } // 用户（轻触触摸屏后）松开，由一个1个MotionEvent ACTION_UP触发
@Override
public boolean onSingleTapUp(MotionEvent e) {
// TODO Auto-generated method stub
Log.i(TAG, "onSingleTapUp..."); return false;
} @Override
public boolean onTouch(View v, MotionEvent event) {
// TODO Auto-generated method stub
Log.i(TAG, "onTouch..."); // Set button visible
mButton01.setVisibility(View.VISIBLE);
mButton02.setVisibility(View.VISIBLE); return mGestureDetector.onTouchEvent(event);
} // @Override
// public boolean onTouchEvent(MotionEvent event) {
// // TODO Auto-generated method stub
// super.onTouchEvent(event);
//
// Log.i(TAG, "onTouchEvent");
// // Set button visible
// mButton01.setVisibility(View.VISIBLE);
// mButton02.setVisibility(View.VISIBLE);
//
// return true;
// } @Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
// TODO Auto-generated method stub
super.onKeyDown(keyCode, event); Log.i(TAG, "onKeyDown...");
// Set button visible
mButton01.setVisibility(View.VISIBLE);
mButton02.setVisibility(View.VISIBLE); return true;
} /* 图片缩小的method */
private void small() {
int bmpWidth=bmp.getWidth();
int bmpHeight=bmp.getHeight(); Log.i(TAG, "bmpWidth = " + bmpWidth + ", bmpHeight = " + bmpHeight); /* 设置图片缩小的比例 */
double scale=0.8;
/* 计算出这次要缩小的比例 */
scaleWidth=(float) (scaleWidth*scale);
scaleHeight=(float) (scaleHeight*scale);
/* 产生reSize后的Bitmap对象 */
Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
Bitmap resizeBmp = Bitmap.createBitmap(bmp,0,0,bmpWidth,
bmpHeight,matrix,true); if(id==0) {
/* 如果是第一次按，就删除原来默认的ImageView */
layoutImage.removeView(mImageView);
} else {
/* 如果不是第一次按，就删除上次放大缩小所产生的ImageView */
layoutImage.removeView((ImageView)findViewById(id));
} /* 产生新的ImageView，放入reSize的Bitmap对象，再放入Layout中 */
id++;
ImageView imageView = new ImageView(this);
imageView.setId(id);
imageView.setImageBitmap(resizeBmp);
layoutImage.addView(imageView);
Log.i(TAG, "imageView.getWidth() = " + imageView.getWidth()
+ ", imageView.getHeight() = " + imageView.getHeight());
setContentView(layout1);
/* 因为图片放到最大时放大按钮会disable，所以在缩小时把它重设为enable */
mButton02.setEnabled(true);
mButton02.setTextColor(Color.MAGENTA);
} /* 图片放大的method */
private void big() {
int bmpWidth=bmp.getWidth();
int bmpHeight=bmp.getHeight(); Log.i(TAG, "bmpWidth = " + bmpWidth + ", bmpHeight = " + bmpHeight); /* 设置图片放大的比例 */
double scale=1.25;
/* 计算这次要放大的比例 */
scaleWidth=(float)(scaleWidth*scale);
scaleHeight=(float)(scaleHeight*scale);
/* 产生reSize后的Bitmap对象 */
Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
Bitmap resizeBmp = Bitmap.createBitmap(bmp,0,0,bmpWidth,
bmpHeight,matrix,true); if(id==0) {
/* 如果是第一次按，就删除原来设置的ImageView */
layoutImage.removeView(mImageView);
} else {
/* 如果不是第一次按，就删除上次放大缩小所产生的ImageView */
layoutImage.removeView((ImageView)findViewById(id));
} /* 产生新的ImageView，放入reSize的Bitmap对象，再放入Layout中 */
id++;
ImageView imageView = new ImageView(this);
imageView.setId(id);
imageView.setImageBitmap(resizeBmp);
layoutImage.addView(imageView);
setContentView(layout1);
/* 如果再放大会超过屏幕大小，就把Button disable */
if( scaleWidth * scale * bmpWidth > bmpWidth * 3 ||
scaleHeight * scale * bmpHeight > bmpWidth * 3 ||
scaleWidth * scale * bmpWidth > displayWidth * 5 ||
scaleHeight * scale * bmpHeight > displayHeight * 5) {
mButton02.setEnabled(false);
mButton02.setTextColor(Color.GRAY);
} else {
mButton02.setEnabled(true);
mButton02.setTextColor(Color.MAGENTA);
}
} }