android 多点触摸图片缩放的具体实现方法
作者：
布局:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/relativeLayout1"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<Button
android:id="@+id/zoom_in"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:text="zoom_in" />
<Button
android:id="@+id/zoom_out"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:text="zoom_out" />
<ScrollView
android:id="@+id/imageContainer"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_below="@+id/zoom_in"
android:fadingEdge="none"
android:scrollbars="none" >
<HorizontalScrollView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_centerHorizontal="true"
android:fadingEdge="none"
android:scrollbars="none" >
<ImageView
android:id="@+id/imageView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:scaleType="matrix" />
</HorizontalScrollView>
</ScrollView>
</RelativeLayout>
程序代码:
package taokun.demo.MutilTouchDemo;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.os.Bundle;
import android.util.FloatMath;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.ImageView;
public class MutilTouchDemoActivity extends Activity implements OnTouchListener, OnClickListener {
private static final String TAG = "Touch" ;
// These matrices will be used to move and zoom image
Matrix matrix = new Matrix();
Matrix savedMatrix = new Matrix();
PointF start = new PointF();
PointF mid = new PointF();
float oldDist;
private ImageView view;
private Button zoomIn, zoomOut;
//button zoom
private float scaleWidth = 1;
private float scaleHeight = 1;
private Bitmap bmp, zoomedBMP;
private int zoom_level = 0;
private static final double ZOOM_IN_SCALE = 1.25;//放大系数
private static final double ZOOM_OUT_SCALE = 0.8;//缩小系数
// We can be in one of these 3 states
static final int NONE = 0;
static final int DRAG = 1;
static final int ZOOM = 2;
int mode = NONE;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//放大按钮
zoomIn = (Button) findViewById(R.id.zoom_in);
//缩小按钮
zoomOut = (Button) findViewById(R.id.zoom_out);
zoomIn.setOnClickListener(this);
zoomOut.setOnClickListener(this);
view = (ImageView) findViewById(R.id.imageView);
view.setOnTouchListener(this);
//取得drawable中图片，放大，缩小，多点触摸的作用对象
bmp = BitmapFactory.decodeResource(MutilTouchDemoActivity.this.getResources(), R.drawable.splash);
}
public boolean onTouch(View v, MotionEvent event) {
// Handle touch events here...
ImageView view = (ImageView) v;
// Handle touch events here...
switch (event.getAction() & MotionEvent.ACTION_MASK) {
//设置拖拉模式
case MotionEvent.ACTION_DOWN:
savedMatrix.set(matrix);
start.set(event.getX(), event.getY());
Log.d(TAG, "mode=DRAG" );
mode = DRAG;
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
mode = NONE;
Log.d(TAG, "mode=NONE" );
break;
//设置多点触摸模式
case MotionEvent.ACTION_POINTER_DOWN:
oldDist = spacing(event);
Log.d(TAG, "oldDist=" + oldDist);
if (oldDist > 10f) {
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
Log.d(TAG, "mode=ZOOM" );
}
break;
//若为DRAG模式，则点击移动图片
case MotionEvent.ACTION_MOVE:
if (mode == DRAG) {
matrix.set(savedMatrix);
// 设置位移
matrix.postTranslate(event.getX() - start.x,
event.getX() - start.x);
}
//若为ZOOM模式，则多点触摸缩放
else if (mode == ZOOM) {
float newDist = spacing(event);
Log.d(TAG, "newDist=" + newDist);
if (newDist > 10f) {
matrix.set(savedMatrix);
float scale = newDist / oldDist;
//设置缩放比例和图片中点位置
matrix.postScale(scale, scale, mid.x, mid.y);
}
}
break;
}
// Perform the transformation
view.setImageMatrix(matrix);
return true; // indicate event was handled
}
//计算移动距离
private float spacing(MotionEvent event) {
float x = event.getX(0) - event.getX(1);
float y = event.getY(0) - event.getY(1);
return FloatMath.sqrt(x * x + y * y);
}
// 计算中点位置
private void midPoint(PointF point, MotionEvent event) {
float x = event.getX(0) + event.getX(1);
float y = event.getY(0) + event.getY(1);
point.set(x / 2, y / 2);
}
//放大，缩小按钮点击事件
@Override
public void onClick(View v) {
if(v == zoomIn){
enlarge();
}else if (v == zoomOut) {
small();
}
}
//按钮点击缩小函数
private void small() {
int bmpWidth = bmp.getWidth();
int bmpHeight = bmp.getHeight();
scaleWidth = (float) (scaleWidth * ZOOM_OUT_SCALE);
scaleHeight = (float) (scaleHeight * ZOOM_OUT_SCALE);
Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
zoomedBMP = Bitmap.createBitmap(bmp, 0, 0, bmpWidth, bmpHeight, matrix,
true);
view.setImageBitmap(zoomedBMP);
}
//按钮点击放大函数
private void enlarge() {
try {
int bmpWidth = bmp.getWidth();
int bmpHeight = bmp.getHeight();
scaleWidth = (float) (scaleWidth * ZOOM_IN_SCALE);
scaleHeight = (float) (scaleHeight * ZOOM_IN_SCALE);
Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
zoomedBMP = Bitmap.createBitmap(bmp, 0, 0, bmpWidth, bmpHeight, matrix,
true);
view.setImageBitmap(zoomedBMP);
} catch (Exception e) {
}
}
}