Android DragImageView实现下拉拖动图片放大效果

DragImageView下拉拖动图片放大，先上图：

主要的类：继承了RelativeLayout，再在RelativeLayout里面添加ImageView，通过Touch事件来改变ImageView的缩放，缩放时计算scale，使其在手指移动到屏幕底部时，图片底部也刚好到达屏幕底部，手指松开时，图片逐步回弹。

package com.example.dragimagescale;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.MotionEvent;
import android.view.WindowManager;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;
import android.widget.RelativeLayout;
public class DragScaleImageView extends RelativeLayout {
private String TAG = "DragScaleImageView";
private static final int BACK_SCALE = 1010;
private Context mContext;
private AttributeSet attrs;
private int displayWidth = 0;
private int displayHeight = 0;
private int mImageId;
private Bitmap bmp;
private ImageView imageView;
/** 是否处在回弹状态 */
private boolean isBacking = false;
/** 用于记录拖拉图片移动的坐标位置 */
private Matrix matrix = new Matrix();
/** 用于记录图片要进行拖拉时候的坐标位置 */
private Matrix currentMatrix = new Matrix();
private Matrix defaultMatrix = new Matrix();
/** 图片的宽高 */
private float imgHeight, imgWidth;
/** 初始状态 */
private int mode = 0;
/** 拖拉照片模式 */
private final int MODE_DRAG = 1;
private float scaleY = 0;
/** 用于记录开始时候的坐标位置 */
private PointF startPoint = new PointF();
/** 用于记录开始时候的在整个屏幕中的Y坐标位置 */
private float startRawY = 0;
float scale = 1;
private TouchEventListener touchEventListener = null;
private BackScaleListener backScaleListener = null;
public DragScaleImageView(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub
this.mContext = context;
this.attrs = attrs;
initView();
}
public DragScaleImageView(Context context) {
super(context);
// TODO Auto-generated constructor stub
this.mContext = context;
initView();
}
public DragScaleImageView(Activity activity, Bitmap resBitmap, int width,
int height) {
super(activity);
}
/**
* 初始化图片
*/
private void initView() {
/* 取得屏幕分辨率大小 */
DisplayMetrics dm = new DisplayMetrics();
WindowManager mWm = (WindowManager) mContext
.getSystemService(Context.WINDOW_SERVICE);
mWm.getDefaultDisplay().getMetrics(dm);
displayWidth = dm.widthPixels;
displayHeight = dm.heightPixels;
TypedArray a = mContext.obtainStyledAttributes(attrs,
R.styleable.DragScaleImageView);
mImageId = a.getResourceId(R.styleable.DragScaleImageView_scale_image,
0);
a.recycle();
if (null == bmp && mImageId != 0) {
bmp = BitmapFactory.decodeResource(getResources(), mImageId);
float scale = (float) displayWidth / (float) bmp.getWidth();// 1080/1800
matrix.postScale(scale, scale, 0, 0);
imgHeight = scale * bmp.getHeight();
imgWidth = scale * bmp.getWidth();
} else {
imgHeight = displayWidth;
imgWidth = displayWidth;
}
initImageView();
}
private void initImageView() {
imageView = new ImageView(mContext);
imageView.setImageMatrix(matrix);
defaultMatrix.set(matrix);
Log.w(TAG, "imgWidth :" + imgWidth);
Log.w(TAG, "imgHeight :" + imgHeight);
RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(
(int) imgWidth, (int) imgHeight);
imageView.setLayoutParams(layoutParams);
imageView.setImageBitmap(bmp);
imageView.setScaleType(ScaleType.CENTER_CROP);
this.addView(imageView);
}
/**
* 设置ImageView的宽高
*
* @param width
* @param height
*/
public void setImageWidthAndHeight(int width, int height) {
imgWidth = width;
imgHeight = height;
RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(
(int) imgWidth, (int) imgHeight);
imageView.setLayoutParams(layoutParams);
}
public boolean onTouchEvent(MotionEvent event) {
Log.w(TAG, "onTouchEvent :" + event.getAction());
// 当该View放置在ScrollView里面时，会与父控件Touch事件冲突，所以touch该控件区域时，父控件不可用
if (event.getAction() == MotionEvent.ACTION_UP) {
getParent().requestDisallowInterceptTouchEvent(false);
} else {
getParent().requestDisallowInterceptTouchEvent(true);// true表示父类的不可用;
}
switch (event.getAction() & MotionEvent.ACTION_MASK) {
// 手指压下屏幕
case MotionEvent.ACTION_DOWN:
if (isBacking) {
return super.onTouchEvent(event);
}
int[] location = new int[2];
imageView.getLocationInWindow(location);
if (location[1] >= 0) {
mode = MODE_DRAG;
// 记录ImageView当前的移动位置
currentMatrix.set(imageView.getImageMatrix());
startPoint.set(event.getX(), event.getY());
startRawY = event.getRawY();
Log.w(TAG, "onTouchEvent startRawY:" + startRawY);
}
break;
// 手指在屏幕上移动，改事件会被不断触发
case MotionEvent.ACTION_MOVE:
// 拖拉图片
if (mode == MODE_DRAG) {
//    float dx = event.getX() - startPoint.x; // 得到x轴的移动距离
float dy = event.getY() - startPoint.y; // 得到y轴的移动距离
// 在没有移动之前的位置上进行移动
if (dy > 0) {
matrix.set(currentMatrix);
Log.w(TAG, "onTouchEvent dy:" + dy);
scale = ((dy / (displayHeight - startRawY) * (displayHeight - imgHeight)) + imgHeight)
/ imgHeight; // 得到缩放倍数，当手指移动到屏幕底部时，图片也达到屏幕底部
Log.w(TAG, "onTouchEvent scale:" + scale);
scaleY = dy;
RelativeLayout.LayoutParams relativeLayout = new RelativeLayout.LayoutParams(
(int) (scale * imgWidth), (int) (scale * imgHeight));
imageView.setLayoutParams(relativeLayout);
matrix.postScale(scale, scale, imgWidth / 2, 0);
imageView.setImageMatrix(matrix);
}
}
break;
// 手指离开屏幕
case MotionEvent.ACTION_UP:
// 当触点离开屏幕，图片还原
mHandler.sendEmptyMessage(BACK_SCALE);
case MotionEvent.ACTION_POINTER_UP:
// 当两个手指移动时，取消移动图片
mode = 0;
break;
}
// 设置的Touch监听事件
if (touchEventListener != null) {
touchEventListener.onTouchEvent(event);
}
return true;
}
/** 逐步回弹 */
@SuppressLint("HandlerLeak")
private Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
switch (msg.what) {
case BACK_SCALE:
scale = (scaleY / 2 + imgHeight) / (imgHeight);// 得到缩放倍数
if (scaleY > 0) {
isBacking = true;
matrix.set(currentMatrix);
RelativeLayout.LayoutParams relativeLayout = new RelativeLayout.LayoutParams(
(int) (scale * imgWidth), (int) (scale * imgHeight));
imageView.setLayoutParams(relativeLayout);
matrix.postScale(scale, scale, imgWidth / 2, 0);
imageView.setImageMatrix(matrix);
scaleY = (float) (scaleY / 2 - 1);
mHandler.sendEmptyMessageDelayed(BACK_SCALE, 20);// 逐步回弹
} else {
scaleY = 0;
RelativeLayout.LayoutParams relativeLayout = new RelativeLayout.LayoutParams(
(int) imgWidth, (int) imgHeight);
imageView.setLayoutParams(relativeLayout);
matrix.set(defaultMatrix);
imageView.setImageMatrix(matrix);
isBacking = false;
}
if (backScaleListener != null) {
backScaleListener.onBackScale();
}
break;
default:
break;
}
super.handleMessage(msg);
}
};
public void setTouchEventListener(TouchEventListener touchEventListener) {
this.touchEventListener = touchEventListener;
}
public void setBackScaleListener(BackScaleListener backScaleListener) {
this.backScaleListener = backScaleListener;
}
/** Touch事件监听 */
public interface TouchEventListener {
public void onTouchEvent(MotionEvent event);
}
/** 回弹事件监听 */
public interface BackScaleListener {
public void onBackScale();
}
}

调用的Activity：

package com.example.dragimagescale;
import com.example.dragimagescale.DragScaleImageView.BackScaleListener;
import com.example.dragimagescale.DragScaleImageView.TouchEventListener;
import android.app.Activity;
import android.os.Bundle;
import android.view.MotionEvent;
public class MainActivity extends Activity {
DragScaleImageView mDragScaleImageView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mDragScaleImageView = (DragScaleImageView) findViewById(R.id.dragScaleImageView);
/** 自定义ImageView的宽高，若不设置则按图片宽高压缩至屏幕宽度 */
//  mDragScaleImageView.setImageWidthAndHeight(720, 300);
// Touch事件监听
mDragScaleImageView.setTouchEventListener(new TouchEventListener() {
@Override
public void onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
// do something here
}
});
// 回弹事件监听
mDragScaleImageView.setBackScaleListener(new BackScaleListener() {
@Override
public void onBackScale() {
// TODO Auto-generated method stub
// do something here
}
});
}
}

xml 布局文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:dragscaleimageview="http://schemas.android.com/apk/res/com.example.dragimagescale"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#ffffff" >
<com.example.dragimagescale.DragScaleImageView
android:id="@+id/dragScaleImageView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
dragscaleimageview:scale_image="@drawable/image"
>
</com.example.dragimagescale.DragScaleImageView>
</RelativeLayout>

下载：源码

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