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;
}
}
};
}