Android学习3: SurfaceView与多线程混搭

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;
            }
        }
    };
}