Android学习3: SurfaceView与多线程混搭

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今天学习了一下Android里面的多线程调用.
使用SurfaceView来显示系统文件夹下面的一些图像.
一个线程来读取图片生成Bitmap, 另个一下线程来绘制图片.
这个例子还是有一些BUG, 生成的Bitmap也可能为空. 产生程序异常.
别外就是改成可以读取任意文件夹下的图片可以绘更好一些.

算了不纠结了, 继续往后看吧.

里面还有一个回调函数.貌似有点不好理解.

sfh.addCallback(new MyCallBack());

layout/activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">    <LinearLayout        android:orientation="horizontal"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:layout_alignParentTop="true"        android:layout_alignParentLeft="true"        android:layout_alignParentStart="true"        android:id="@+id/linearLayout">        <Button            android:layout_width="120dp"            android:layout_height="40dp"            android:text="启动多线程"            android:id="@+id/button" />    </LinearLayout>    <SurfaceView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:id="@+id/surfaceView"        android:layout_below="@+id/linearLayout"        android:layout_alignParentLeft="true"        android:layout_alignParentStart="true"        android:layout_alignParentBottom="true"        android:layout_alignParentRight="true"        android:layout_alignParentEnd="true" /></RelativeLayout>

com/example/youtwo/testthread/MainActivity.java

package com.example.youtwo.testthread;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.PorterDuff;import android.graphics.PorterDuffXfermode;import android.graphics.Rect;import android.graphics.RectF;import android.support.v7.app.ActionBarActivity;import android.os.Bundle;import android.util.DisplayMetrics;import android.util.Log;import android.view.Menu;import android.view.MenuItem;import android.view.SurfaceHolder;import android.view.SurfaceView;import android.view.View;import android.widget.Button;import java.lang.reflect.Field;import java.util.ArrayList;public class MainActivity extends ActionBarActivity {    Button btnDoubleThread;    SurfaceView sfv;    SurfaceHolder sfh;    int imgWidth, imgHeight;    ArrayList imgList = new ArrayList();    Bitmap bitmap;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        // 初始化按钮        btnDoubleThread = (Button) this.findViewById(R.id.button);        btnDoubleThread.setOnClickListener(new ClickEvent());        // 初始化绘图容器        sfv = (SurfaceView) this.findViewById(R.id.surfaceView);        sfh = sfv.getHolder();        // 自动运行surfaceCreated以及surfaceChanged        sfh.addCallback(new MyCallBack());        bitmap = null;    }    @Override    public boolean onCreateOptionsMenu(Menu menu) {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.menu_main, menu);        return true;    }    @Override    public boolean onOptionsItemSelected(MenuItem item) {        // Handle action bar item clicks here. The action bar will        // automatically handle clicks on the Home/Up button, so long        // as you specify a parent activity in AndroidManifest.xml.        int id = item.getItemId();        //noinspection SimplifiableIfStatement        if (id == R.id.action_settings) {            return true;        }        return super.onOptionsItemSelected(item);    }    class ClickEvent implements View.OnClickListener {        @Override        public void onClick(View v) {            if (v == btnDoubleThread) {                new LoadImage().start();//开一条线程读取                new DrawImage(imgWidth + 10, 0).start();//开一条线程绘图            }        }    };    class MyCallBack implements SurfaceHolder.Callback {        @Override        public void surfaceChanged(SurfaceHolder holder, int format, int width,                                   int height) {            Log.i("Surface:", "Change");        }        @Override        public void surfaceCreated(SurfaceHolder holder) {            Log.i("Surface:", "Create");            // 用反射机制来获取资源中的图片ID和尺寸            Field[] fields = R.drawable.class.getDeclaredFields();            for (Field field : fields) {                if (!"icon".equals(field.getName()))// 除了icon之外的图片                {                    int index = 0;                    try {                        index = field.getInt(R.drawable.class);                    } catch (IllegalArgumentException e) {                        // TODO Auto-generated catch block                        e.printStackTrace();                    } catch (IllegalAccessException e) {                        // TODO Auto-generated catch block                        e.printStackTrace();                    }                    // 保存图片ID                    imgList.add(index);                }            }            // 取得图像大小            Bitmap bmImg = BitmapFactory.decodeResource(getResources(),                    (Integer) imgList.get(0));            imgWidth = bmImg.getWidth();            imgHeight = bmImg.getHeight();        }        @Override        public void surfaceDestroyed(SurfaceHolder holder) {            Log.i("Surface:", "Destroy");        }    };    /*     * 只负责绘图的线程     */    class DrawImage extends Thread {        int x, y;        public DrawImage(int x, int y) {            this.x = x;            this.y = y;        }        public void run() {            while (true) {                if (bitmap != null) {//如果图像有效                    // 获取屏幕大小                    DisplayMetrics dm = new DisplayMetrics();                    getWindowManager().getDefaultDisplay().getMetrics(dm);                    Canvas c = sfh.lockCanvas(new Rect(this.x, this.y,                            dm.widthPixels, dm.heightPixels));                    Paint mPaint = new Paint();                    // 清除屏幕                    mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));                    c.drawPaint(mPaint);                    mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));                    if(bitmap != null) {                        // 把系统图标缩放到当前窗口的大小显示                        Rect src = new Rect(0,0,bitmap.getWidth(), bitmap.getHeight());                        RectF dst = new RectF(0,0,dm.widthPixels,dm.heightPixels);                        c.drawBitmap(bitmap, src, dst, mPaint);                    }                    sfh.unlockCanvasAndPost(c);// 更新屏幕显示内容                }            }        }    };    /*     * 只负责读取图片的线程     */    class LoadImage extends Thread {        int imgIndex = 0;        public void run() {            while (true) {                bitmap = BitmapFactory.decodeResource(getResources(),                        (Integer) imgList.get(imgIndex));                imgIndex++;                if (imgIndex == imgList.size())//如果到尽头则重新读取                    imgIndex = 0;            }        }    };}

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