android 实现图片加载效果

先贴图：
代码如下：

package com.android.activity;import java.text.DecimalFormat;import android.content.Context;import android.content.res.TypedArray;import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.PorterDuff;import android.graphics.PorterDuffXfermode;import android.graphics.drawable.BitmapDrawable;import android.graphics.drawable.Drawable;import android.util.AttributeSet;import android.util.Log;import android.widget.ImageView;/** * 自定义组件实现新浪微博的图片加载效果。
 *  *  *  */public class PorterDuffView extends ImageView {private static final String TAG = "PorterDuffView";/** 前景Bitmap高度为1像素。采用循环多次填充进度区域。 */public static final int FG_HEIGHT = 1;/** 下载进度前景色 （铺上的红色）*/// public static final int FOREGROUND_COLOR = 0x77123456;public static final int FOREGROUND_COLOR = 0x77ff0000;/** 下载进度条文字颜色。 */public static final int TEXT_COLOR = 0xff7fff00;/** 进度百分比字体大小。 */public static final int FONT_SIZE = 30;private Bitmap bitmapBg, bitmapFg;private Paint paint;/** 标识当前进度。 */private float progress;/** 标识进度图片的宽度与高度。 */private int width, height;/** 格式化输出百分比。 */private DecimalFormat decFormat;/** 进度百分比文本的锚定Y中心坐标值。 */private float txtBaseY;/** 标识是否使用PorterDuff模式重组界面。 */private boolean porterduffMode;/** 标识是否正在下载图片。 */private boolean loading;public PorterDuffView(Context context, AttributeSet attrs) {super(context, attrs);init(context, attrs);}/** 生成一宽与背景图片等同高为1像素的Bitmap，。 */private static Bitmap createForegroundBitmap(int w) {Bitmap bm = Bitmap.createBitmap(w, FG_HEIGHT, Bitmap.Config.ARGB_8888);Canvas c = new Canvas(bm);Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);p.setColor(FOREGROUND_COLOR);c.drawRect(0, 0, w, FG_HEIGHT, p);return bm;}private void init(Context context, AttributeSet attrs) {if (attrs != null) {TypedArray typedArr = context.obtainStyledAttributes(attrs,R.styleable.PorterDuffView);porterduffMode = typedArr.getBoolean(R.styleable.PorterDuffView_porterduffMode, false);}Drawable drawable = getDrawable();if (porterduffMode && drawable != null&& drawable instanceof BitmapDrawable) {bitmapBg = ((BitmapDrawable) drawable).getBitmap();width = bitmapBg.getWidth();height = bitmapBg.getHeight();bitmapFg = createForegroundBitmap(width);//得到高度为1的红色前景色} else {// 不符合要求，自动设置为false。porterduffMode = false;}paint = new Paint();paint.setFilterBitmap(false);paint.setAntiAlias(true);paint.setTextSize(FONT_SIZE);Paint.FontMetrics fontMetrics = paint.getFontMetrics();// 注意观察本输出：// ascent:单个字符基线以上的推荐间距，为负数Log.i(TAG, "ascent:" + fontMetrics.ascent//// descent:单个字符基线以下的推荐间距，为正数+ " descent:" + fontMetrics.descent //// 单个字符基线以上的最大间距，为负数+ " top:" + fontMetrics.top //// 单个字符基线以下的最大间距，为正数+ " bottom:" + fontMetrics.bottom//// 文本行与行之间的推荐间距+ " leading:" + fontMetrics.leading);// 在此处直接计算出来，避免了在onDraw()处的重复计算txtBaseY = (height - fontMetrics.bottom - fontMetrics.top) / 2;decFormat = new DecimalFormat("0.0%");}public void onDraw(Canvas canvas) {if (porterduffMode) {int tmpW = (getWidth() - width) / 2, tmpH = (getHeight() - height) / 2;// 画出背景图canvas.drawBitmap(bitmapBg, tmpW, tmpH, paint);// 设置PorterDuff模式paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DARKEN));// canvas.drawBitmap(bitmapFg, tmpW, tmpH - progress * height,// paint);int tH = height - (int) (progress * height);for (int i = 0; i < tH; i++) {canvas.drawBitmap(bitmapFg, tmpW, tmpH + i, paint);}// 立即取消xfermodepaint.setXfermode(null);int oriColor = paint.getColor();paint.setColor(TEXT_COLOR);paint.setTextSize(FONT_SIZE);String tmp = decFormat.format(progress);float tmpWidth = paint.measureText(tmp);canvas.drawText(decFormat.format(progress), tmpW+ (width - tmpWidth) / 2, tmpH + txtBaseY, paint);// 恢复为初始值时的颜色paint.setColor(oriColor);} else {Log.i(TAG, "onDraw super");super.onDraw(canvas);}}public void setProgress(float progress) {if (porterduffMode) {this.progress = progress;// 刷新自身。invalidate();}}public boolean isLoading() {return loading;}public void setLoading(boolean loading) {this.loading = loading;}public void setPorterDuffMode(boolean bool) {porterduffMode = bool;}}

//图片加载类

package com.android.activity;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.InputStream;import org.apache.http.Header;import org.apache.http.HttpEntity;import org.apache.http.HttpResponse;import org.apache.http.client.ClientProtocolException;import org.apache.http.client.HttpClient;import org.apache.http.client.methods.HttpGet;import org.apache.http.impl.client.DefaultHttpClient;import org.apache.http.params.HttpParams;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.os.AsyncTask;import android.util.Log;public class DownloadImgTask extends AsyncTask {private static final String TAG="DownloadImgTask";    private PorterDuffView pdView;                public DownloadImgTask(PorterDuffView pdView) {                this.pdView = pdView;        }        /** 下载准备工作。在UI线程中调用。 */        protected void onPreExecute() {        Log.i(TAG, "onPreExecute");        }        /** 执行下载。在背景线程调用。 */        protected Bitmap doInBackground(String... params) {        Log.i(TAG, "doInBackground:" + params[0]);                HttpClient httpClient = new DefaultHttpClient();                HttpGet httpGet = new HttpGet(params[0]);                InputStream is = null;                ByteArrayOutputStream baos = null;                try {                        HttpResponse httpResponse = httpClient.execute(httpGet);                        printHttpResponse(httpResponse);                        HttpEntity httpEntity = httpResponse.getEntity();                        long length = httpEntity.getContentLength();                        Log.i(TAG, "content length=" + length);                        is = httpEntity.getContent();                        if (is != null) {                                baos = new ByteArrayOutputStream();                                byte[] buf = new byte[128];                                int read = -1;                                int count = 0;                                while ((read = is.read(buf)) != -1) {                                        baos.write(buf, 0, read);                                        count += read;                                        publishProgress(count * 1.0f / length);                                }                                Log.i(TAG, "count=" + count + " length=" + length);                                byte[] data = baos.toByteArray();                                Bitmap bit = BitmapFactory.decodeByteArray(data, 0, data.length);                                return bit;                        }                } catch (ClientProtocolException e) {                        e.printStackTrace();                } catch (IOException e) {                        e.printStackTrace();                } finally {                        try {                                if (baos != null) {                                        baos.close();                                }                                if (is != null) {                                        is.close();                                }                        } catch (IOException e) {                                e.printStackTrace();                        }                }                return null;        }        /** 更新下载进度。在UI线程调用。onProgressUpdate */        protected void onProgressUpdate(Float... progress) {                pdView.setProgress(progress[0]);        }        /** 通知下载任务完成。在UI线程调用。 */        protected void onPostExecute(Bitmap bit) {        Log.i(TAG, "onPostExecute");                pdView.setPorterDuffMode(false);                pdView.setLoading(false);                pdView.setImageBitmap(bit);        }        protected void onCancelled() {        Log.i(TAG, "DownloadImgTask cancel...");                super.onCancelled();        }        private void printHttpResponse(HttpResponse httpResponse) {                Header[] headerArr = httpResponse.getAllHeaders();                for (int i = 0; i < headerArr.length; i++) {                        Header header = headerArr[i];                        Log.i(TAG, "name[" + header.getName() + "]value[" + header.getValue() + "]");                }                HttpParams params = httpResponse.getParams();                Log.i(TAG, String.valueOf(params));                Log.i(TAG, String.valueOf(httpResponse.getLocale()));        }}

//主activity

package com.android.activity;import android.app.Activity;import android.os.Bundle;public class ActAsyncTaskActivity extends Activity{    private PorterDuffView pViewA;    public static final String[] STRING_ARR = {//    "http://developer.android.com/images/home/android-jellybean.png",//                    "http://developer.android.com/images/home/design.png",//                    "http://developer.android.com/images/home/google-play.png",//                    "http://developer.android.com/images/home/google-io.png" };    public void onCreate(Bundle savedInstanceState) {            super.onCreate(savedInstanceState);            setContentView(R.layout.main);            pViewA = (PorterDuffView) findViewById(R.id.pViewA);                        if (pViewA.isLoading() == false) {                DownloadImgTask task = new DownloadImgTask(pViewA);                task.execute(STRING_ARR[pViewA.getId() % STRING_ARR.length]);                pViewA.setPorterDuffMode(true);                pViewA.setLoading(true);                pViewA.setProgress(0);                pViewA.invalidate();        }    }}

//main.xml

<?xml version="1.0" encoding="utf-8"?>

附上源码下载地址：

http://download.csdn.net/detail/duanyu218/5046973

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