Android学习2: Android使用SurfaceView绘制一条移动的线段

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今天学习了一下, 怎样使用 SurfaceView. SurfaceHolder, Canvas 和 Paint 来绘制一条移动的线段

例子, 都是我从网上找的, 只不过是自已简化了一些, 改掉了一些过时的代码.都不是原创的, 只不过能明白原理就好

这个例子在运行时, 还有内存泄露.我怀疑是在执行SimpleDraw() 函数的时候产生的.

不过现在还没法改.

定时器再次启动时, 需要重置TimerTask, 因为一个TimerTask只能执行一次, 一次性的.

代码:

布局文件:

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="vertical"        android:layout_width="fill_parent"        android:layout_height="fill_parent"        android:layout_alignParentLeft="true"        android:layout_alignParentStart="true">        <LinearLayout            android:orientation="horizontal"            android:layout_width="match_parent"            android:layout_height="wrap_content">            <Button                android:layout_width="150dp"                android:layout_height="45dp"                android:text="定时器绘图"                android:id="@+id/button2" />        </LinearLayout>        <SurfaceView            android:layout_width="match_parent"            android:layout_height="match_parent"            android:id="@+id/surfaceView"            android:layout_gravity="center_horizontal" />    </LinearLayout></RelativeLayout>

com/example/youtwo/testsurfaceview/MainActivity.java

package com.example.youtwo.testsurfaceview;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.PorterDuff;import android.graphics.PorterDuffXfermode;import android.graphics.Rect;import android.support.v7.app.ActionBarActivity;import android.os.Bundle;import android.util.DisplayMetrics;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.util.Timer;import java.util.TimerTask;public class MainActivity extends ActionBarActivity {    // 按钮    private Button btnTimerDraw;    // 绘图容器    private SurfaceView sfv;    private SurfaceHolder sfh;    // 定时器    private Timer mTimer;    private MyTimerTask mTimerTask;    // 坐标    private int pos_h;    // 屏幕大小    DisplayMetrics dm;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        // 初始化按钮&绑定按钮点击事件        btnTimerDraw = (Button) this.findViewById(R.id.button2);        btnTimerDraw.setOnClickListener(new ClickEvent());        // 初始化绘图容器        sfv = (SurfaceView) this.findViewById(R.id.surfaceView);        sfh = sfv.getHolder();        // 初始化定时器        mTimer = new Timer();        mTimerTask = new MyTimerTask();        // 初始化坐标        pos_h = 0;        // 获取屏幕大小        dm = new DisplayMetrics();        getWindowManager().getDefaultDisplay().getMetrics(dm);    }    @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);    }    // 事件接收    class ClickEvent implements View.OnClickListener {        @Override        public void onClick(View v) {            if (v == btnTimerDraw) {                mTimerTask = new MyTimerTask();                mTimer.schedule(mTimerTask, 0, 5);//动态绘制            }        }    }    // 绘制类    class MyTimerTask extends TimerTask {        @Override        public void run() {            SimpleDraw(pos_h);            pos_h += 5;            // 如果高度大于屏幕高度            if (pos_h >= dm.heightPixels) {                pos_h = 0;            }        }    }    /*    * 绘制指定区域    */    void SimpleDraw(int pos_h) {        // 初始化画布,这步是关键        Canvas canvas = sfh.lockCanvas(new Rect(0, 0,                dm.widthPixels, dm.heightPixels));        // 初始化画笔        Paint mPaint = new Paint();        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));        canvas.drawPaint(mPaint);        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));        mPaint.setColor(Color.GREEN);// 画笔为绿色        mPaint.setStrokeWidth(5);// 设置画笔粗细        // 绘制线段        canvas.drawLine(0, pos_h, dm.widthPixels, pos_h, mPaint);        sfh.unlockCanvasAndPost(canvas);// 解锁画布，提交画好的图像        mPaint.reset();    }}

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