21天學習android開發教程之SurfaceView與多線程的混搭

上一篇簡單介紹了SurfaceView的基本使用，這次就介紹SurfaceView與多線程的混搭。SurfaceView與多線程混搭，是為了防止動畫閃爍而實現的一種多線程應用。android的多線程用法與JAVA的多線程用法完全一樣，本文不做多線程方面的介紹了。直接講解SurfaceView與多線程的混合使用，即開一條線程專門讀取圖片，另外一條線程專門繪圖。
        本文程序運行截圖如下，左邊是開單個線程讀取並繪圖，右邊是開兩個線程，一個專門讀取圖片，一個專門繪圖：

對比一下，右邊動畫的幀速明顯比左邊的快，左右兩者都沒使用Thread.sleep()。為什麼要開兩個線程一個讀一個畫，而不去開兩個線程像左邊那樣都“邊讀邊畫”呢？因為SurfaceView每次繪圖都會鎖定Canvas,也就是說同一片區域這次沒畫完下次就不能畫，因此要提高動畫播放的效率，就得開一條線程專門畫圖，開另外一條線程做預處理的工作。
main.xml的源碼：

<linearlayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" android:layout_height="fill_parent"
    android:orientation="vertical">

    <linearlayout android:id="@+id/LinearLayout01" 
        android:layout_width="wrap_content" android:layout_height="wrap_content">
        <button android:id="@+id/Button01" android:layout_width="wrap_content" 
            android:layout_height="wrap_content" android:text="單個獨立線程">
        <button android:id="@+id/Button02" android:layout_width="wrap_content" 
            android:layout_height="wrap_content" android:text="兩個獨立線程">
    
    <surfaceview android:id="@+id/SurfaceView01" 
        android:layout_width="fill_parent" android:layout_height="fill_parent">

本文程序的源碼：

package com.testSurfaceView;

import java.lang.reflect.Field;
import java.util.ArrayList;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.Button;

public class testSurfaceView extends Activity {
    /** Called when the activity is first created. */
    Button btnSingleThread, btnDoubleThread;
    SurfaceView sfv;
    SurfaceHolder sfh;
    ArrayList imgList = new ArrayList();
    int imgWidth, imgHeight;
    Bitmap bitmap;//獨立線程讀取，獨立線程繪圖

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        btnSingleThread = (Button) this.findViewById(R.id.Button01);
        btnDoubleThread = (Button) this.findViewById(R.id.Button02);
        btnSingleThread.setOnClickListener(new ClickEvent());
        btnDoubleThread.setOnClickListener(new ClickEvent());
        sfv = (SurfaceView) this.findViewById(R.id.SurfaceView01);
        sfh = sfv.getHolder();
        sfh.addCallback(new MyCallBack());// 自動運行surfaceCreated以及surfaceChanged
    }

    class ClickEvent implements View.OnClickListener {

        @Override
        public void onClick(View v) {

            if (v == btnSingleThread) {
                new Load_DrawImage(0, 0).start();//開一條線程讀取並繪圖
            } else if (v == btnDoubleThread) {
                new LoadImage().start();//開一條線程讀取
                new DrawImage(imgWidth + 10, 0).start();//開一條線程繪圖
            }

        }

    }

    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");

            // 用反射機制來獲取資源中的圖片ID和尺寸
            Field[] fields = R.drawable.class.getDeclaredFields();
            for (Field field : fields) {
                if (!"icon".equals(field.getName()))// 除了icon之外的圖片
                {
                    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();
                    }
                    // 保存圖片ID
                    imgList.add(index);
                }
            }
            // 取得圖像大小
            Bitmap bmImg = BitmapFactory.decodeResource(getResources(),
                    imgList.get(0));
            imgWidth = bmImg.getWidth();
            imgHeight = bmImg.getHeight();
        }

        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
            Log.i("Surface:", "Destroy");

        }

    }

    /*
     * 讀取並顯示圖片的線程
     */
    class Load_DrawImage extends Thread {
        int x, y;
        int imgIndex = 0;

        public Load_DrawImage(int x, int y) {
            this.x = x;
            this.y = y;
        }

        public void run() {
            while (true) {
                Canvas c = sfh.lockCanvas(new Rect(this.x, this.y, this.x
                        + imgWidth, this.y + imgHeight));
                Bitmap bmImg = BitmapFactory.decodeResource(getResources(),
                        imgList.get(imgIndex));
                c.drawBitmap(bmImg, this.x, this.y, new Paint());
                imgIndex++;
                if (imgIndex == imgList.size())
                    imgIndex = 0;

                sfh.unlockCanvasAndPost(c);// 更新屏幕顯示內容
            }
        }
    };

    /*
     * 只負責繪圖的線程
     */
    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) {//如果圖像有效
                    Canvas c = sfh.lockCanvas(new Rect(this.x, this.y, this.x
                            + imgWidth, this.y + imgHeight));

                    c.drawBitmap(bitmap, this.x, this.y, new Paint());

                    sfh.unlockCanvasAndPost(c);// 更新屏幕顯示內容
                }
            }
        }
    };

    /*
     * 只負責讀取圖片的線程
     */
    class LoadImage extends Thread {
        int imgIndex = 0;

        public void run() {
            while (true) {
                bitmap = BitmapFactory.decodeResource(getResources(),
                        imgList.get(imgIndex));
                imgIndex++;
                if (imgIndex == imgList.size())//如果到盡頭則重新讀取
                    imgIndex = 0;
            }
        }
    };
}

以上就是本文的全部內容，希望對大家學習Android軟件編程有所幫助。