图片浏览、缩放、拖动、自动居中代码,Java代码库,德仔网

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【Java】图片浏览、缩放、拖动、自动居中
作者:fth826595345 / 发布于2013/10/23/ 556

	布局文件
	<?xml version="1.0" encoding="utf-8"?>
	<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:layout_width="fill_parent"
	android:layout_height="fill_parent"
	android:layout_gravity="center">
	
	<ImageView android:id="@+id/imageView"
	 android:layout_width="fill_parent"
	 android:layout_height="fill_parent"
	 android:scaleType="matrix"
	 android:layout_gravity="center">
	</ImageView>
	
	</FrameLayout>

	

	package cn.edu.scau.util;

	import android.app.Activity;
	import android.content.Intent;
	import android.graphics.Bitmap;
	import android.graphics.BitmapFactory;
	import android.graphics.Matrix;
	import android.graphics.PointF;
	import android.graphics.RectF;
	import android.os.Bundle;
	import android.util.DisplayMetrics;
	import android.util.FloatMath;
	import android.view.KeyEvent;
	import android.view.MotionEvent;
	import android.view.View;
	import android.view.Window;
	import android.view.View.OnTouchListener;
	import android.widget.ImageView;

	public class MultiTouch extends Activity implements OnTouchListener {
	/**
	 * 图片浏览、缩放、拖动、自动居中
	 */
	private int resource_id;
	Matrix matrix = new Matrix();
	Matrix savedMatrix = new Matrix();
	DisplayMetrics dm;
	ImageView imgView;
	Bitmap bitmap;

	float minScaleR;// 最小缩放比例
	static final float MAX_SCALE = 4f;// 最大缩放比例

	static final int NONE = 0;// 初始状态
	static final int DRAG = 1;// 拖动
	static final int ZOOM = 2;// 缩放
	int mode = NONE;

	PointF prev = new PointF();
	PointF mid = new PointF();
	float dist = 1f;

	@Override
	public void onCreate(Bundle savedInstanceState) {
	 super.onCreate(savedInstanceState);
	 requestWindowFeature(Window.FEATURE_NO_TITLE);
	 setContentView(R.layout.multitouch);
	
	 Intent intent = this.getIntent();
	 Bundle bundle = intent.getExtras();
	 resource_id = bundle.getInt("id");
	
	 imgView = (ImageView) findViewById(R.id.imageView);// 获取控件
	 bitmap = BitmapFactory.decodeResource(getResources(),
	 resource_id);// 获取图片资源
	 imgView.setImageBitmap(bitmap);// 填充控件
	 imgView.setOnTouchListener(this);// 设置触屏监听
	 dm = new DisplayMetrics();
	 getWindowManager().getDefaultDisplay().getMetrics(dm);// 获取分辨率
	 minZoom();
	 center();
	 imgView.setImageMatrix(matrix);
	}

	/**
	 * 触屏监听
	 */
	public boolean onTouch(View v, MotionEvent event) {

	 switch (event.getAction() & MotionEvent.ACTION_MASK) {
	 // 主点按下
	 case MotionEvent.ACTION_DOWN:
	 savedMatrix.set(matrix);
	 prev.set(event.getX(), event.getY());
	 mode = DRAG;
	 break;
	 // 副点按下
	 case MotionEvent.ACTION_POINTER_DOWN:
	 dist = spacing(event);
	 // 如果连续两点距离大于10，则判定为多点模式
	 if (spacing(event) > 10f) {
	 savedMatrix.set(matrix);
	 midPoint(mid, event);
	 mode = ZOOM;
	 }
	 break;
	 case MotionEvent.ACTION_UP:
	 case MotionEvent.ACTION_POINTER_UP:
	 mode = NONE;
	 break;
	 case MotionEvent.ACTION_MOVE:
	 if (mode == DRAG) {
	 matrix.set(savedMatrix);
	 matrix.postTranslate(event.getX() - prev.x, event.getY()
	 - prev.y);
	 } else if (mode == ZOOM) {
	 float newDist = spacing(event);
	 if (newDist > 10f) {
	 matrix.set(savedMatrix);
	 float tScale = newDist / dist;
	 matrix.postScale(tScale, tScale, mid.x, mid.y);
	 }
	 }
	 break;
	 }
	 imgView.setImageMatrix(matrix);
	 CheckView();
	 return true;
	}

	/**
	 * 限制最大最小缩放比例，自动居中
	 */
	private void CheckView() {
	 float p[] = new float[9];
	 matrix.getValues(p);
	 if (mode == ZOOM) {
	 if (p[0] < minScaleR) {
	 matrix.setScale(minScaleR, minScaleR);
	 }
	 if (p[0] > MAX_SCALE) {
	 matrix.set(savedMatrix);
	 }
	 }
	 center();
	}

	/**
	 * 最小缩放比例，最大为100%
	 */
	private void minZoom() {
	 minScaleR = Math.min(
	 (float) dm.widthPixels / (float) bitmap.getWidth(),
	 (float) dm.heightPixels / (float) bitmap.getHeight());
	 if (minScaleR < 1.0) {
	 matrix.postScale(minScaleR, minScaleR);
	 }
	}

	private void center() {
	 center(true, true);
	}

	/**
	 * 横向、纵向居中
	 */
	protected void center(boolean horizontal, boolean vertical) {

	 Matrix m = new Matrix();
	 m.set(matrix);
	 RectF rect = new RectF(0, 0, bitmap.getWidth(), bitmap.getHeight());
	 m.mapRect(rect);

	 float height = rect.height();
	 float width = rect.width();

	 float deltaX = 0, deltaY = 0;

	 if (vertical) {
	 // 图片小于屏幕大小，则居中显示。大于屏幕，上方留空则往上移，下方留空则往下移
	 int screenHeight = dm.heightPixels;
	 if (height < screenHeight) {
	 deltaY = (screenHeight - height) / 2 - rect.top;
	 } else if (rect.top > 0) {
	 deltaY = -rect.top;
	 } else if (rect.bottom < screenHeight) {
	 deltaY = imgView.getHeight() - rect.bottom;
	 }
	 }

	 if (horizontal) {
	 int screenWidth = dm.widthPixels;
	 if (width < screenWidth) {
	 deltaX = (screenWidth - width) / 2 - rect.left;
	 } else if (rect.left > 0) {
	 deltaX = -rect.left;
	 } else if (rect.right < screenWidth) {
	 deltaX = screenWidth - rect.right;
	 }
	 }
	 matrix.postTranslate(deltaX, deltaY);
	}

	/**
	 * 两点的距离
	 */
	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);
	}

	/**
	 * 两点的中点
	 */
	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);
	}
	
	//监听返回键
	public boolean onKeyDown(int keyCode, KeyEvent event) {
	 if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
	 this.finish();
	 //设置切换动画，从左边进入，右边退出
	 overridePendingTransition(R.anim.in_from_left, R.anim.out_to_right);
	 return true;
	 }
	 return super.onKeyDown(keyCode, event);
	}
	}
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