自定义imageview，实现仿微信的气泡型的图片

package com.padandroid.wechat.widget;import java.lang.ref.WeakReference;import android.annotation.SuppressLint;import android.content.Context;import android.content.res.TypedArray;import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.PorterDuff;import android.graphics.PorterDuffXfermode;import android.graphics.Xfermode;import android.graphics.drawable.Drawable;import android.util.AttributeSet;import com.padandroid.wechat.R;public class ChatImageView extends MyImageView {private Context mContext;private static final Xfermode sXfermode = new PorterDuffXfermode(PorterDuff.Mode.DST_IN);private Bitmap mMaskBitmap;private Paint mPaint;private WeakReference<Bitmap> mSrcWeakBitmap;private int mLastWidth;private int mLastHeight;private int maskRes;public ChatImageView(Context context, AttributeSet attrs) {super(context, attrs);mContext = context;mPaint = new Paint();TypedArray a = context.obtainStyledAttributes(attrs,R.styleable.ChatImageView);maskRes = a.getResourceId(R.styleable.ChatImageView_mask_res, -1);a.recycle();}public void invalidate() {mSrcWeakBitmap = null;if (mMaskBitmap != null) {mMaskBitmap.recycle();}mLastWidth = 0;mLastHeight = 0;super.invalidate();}@SuppressLint("DrawAllocation")@Overrideprotected void onDraw(Canvas canvas) {if (!isInEditMode()) {int width = getWidth();int height = getHeight();int i = canvas.saveLayer(0.0F, 0.0F, width, height, null,Canvas.ALL_SAVE_FLAG);try {Bitmap srcBitmap = mSrcWeakBitmap != null ? mSrcWeakBitmap.get() : null;if (srcBitmap == null || srcBitmap.isRecycled()) {Drawable srcDrawable = getDrawable();if (srcDrawable != null) {srcBitmap = Bitmap.createBitmap(getWidth(),getHeight(), Bitmap.Config.ARGB_8888);Canvas srcBitmapCanvas = new Canvas(srcBitmap);srcDrawable.setBounds(0, 0, getWidth(), getHeight());srcDrawable.draw(srcBitmapCanvas);if (mMaskBitmap == null || mMaskBitmap.isRecycled()|| mLastWidth != width || mLastHeight != height) {mMaskBitmap = getMask(width, height);}drawBitmap(srcBitmapCanvas, mMaskBitmap, mPaint);mSrcWeakBitmap = new WeakReference<Bitmap>(srcBitmap);}}if (srcBitmap != null) {mPaint.setXfermode(null);canvas.drawBitmap(srcBitmap, 0.0F, 0.0F, mPaint);}} catch (Exception e) {System.gc();} finally {canvas.restoreToCount(i);}} else {super.onDraw(canvas);}}public void drawBitmap(Canvas canvas, Bitmap bitmap, Paint paint) {paint.reset();paint.setFilterBitmap(false);paint.setXfermode(sXfermode);canvas.drawBitmap(bitmap, 0, 0, paint);}private Bitmap getMask(int width, int height) {Bitmap bitmap = Bitmap.createBitmap(width, height,Bitmap.Config.ARGB_8888);Canvas canvas = new Canvas(bitmap);Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);paint.setColor(Color.BLACK);Drawable mask = mContext.getResources().getDrawable(maskRes);mask.setBounds(0, 0, width, height);mask.draw(canvas);return bitmap;}}