上次介绍MediaPlayer的时候稍微介绍了SurfaceView,SurfaceView由于可以直接从内存或者DMA等硬件接口取得图像数据,因此是个非常重要的绘图容器,这次我就用两篇文章来介绍SurfaceView的用法。网上介绍SurfaceView的用法有很多,写法也层出不同,例如继承SurfaceView类,或者继承SurfaceHolder.Callback类等,这个可以根据功能实际需要自己选择,我这里就直接在普通的用户界面调用SurfaceHolder的lockCanvas和unlockCanvasAndPost。
先来看看程序运行的截图:
使用方法" />
截图1主要演示了直接把正弦波绘画在SurfaceView上
对比上面的左右两图,右图用.lockCanvas(null),而左图用.lockCanvas(new Rect(oldX, 0, oldX + length, getWindowManager().getDefaultDisplay().getHeight())),对比一下两个效果,由于左图是按指定Rect绘画,所以效率会比右图的全控件绘画高些,并且在清屏之后(canvas.drawColor(Color.BLACK))不会留有上次绘画的残留。
接下来贴出main.xml的源码:
XML/
HTML代码
class="dp-xml" start="1">
- <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="简单绘画">
- <button android:id="@+id/Button02" android:layout_width="wrap_content"
- android:layout_height="wrap_content" android:text="定时器绘画">
-
- <surfaceview android:id="@+id/SurfaceView01"
- android:layout_width="fill_parent" android:layout_height="fill_parent">
接下来贴出程序源码:
Java代码
- package com.testSurfaceView;
-
- import java.util.Timer;
- import java.util.TimerTask;
-
- import android.app.Activity;
- import android.graphics.Canvas;
- import android.graphics.Color;
- 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 {
-
- Button btnSimpleDraw, btnTimerDraw;
- SurfaceView sfv;
- SurfaceHolder sfh;
-
- private Timer mTimer;
- private MyTimerTask mTimerTask;
- int Y_axis[],
- centerY,
- oldX,oldY,
- currentX;
-
- @Override
- public void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
-
- btnSimpleDraw = (Button) this.findViewById(R.id.Button01);
- btnTimerDraw = (Button) this.findViewById(R.id.Button02);
- btnSimpleDraw.setOnClickListener(new ClickEvent());
- btnTimerDraw.setOnClickListener(new ClickEvent());
- sfv = (SurfaceView) this.findViewById(R.id.SurfaceView01);
- sfh = sfv.getHolder();
-
-
- mTimer = new Timer();
- mTimerTask = new MyTimerTask();
-
-
- centerY = (getWindowManager().getDefaultDisplay().getHeight() - sfv
- .getTop()) / 2;
- Y_axis = new int[getWindowManager().getDefaultDisplay().getWidth()];
- for (int i = 1; i < Y_axis.length; i++) {
- Y_axis[i - 1] = centerY
- - (int) (100 * Math.sin(i * 2 * Math.PI / 180));
- }
- }
-
- class ClickEvent implements View.OnClickListener {
-
- @Override
- public void onClick(View v) {
-
- if (v == btnSimpleDraw) {
- SimpleDraw(Y_axis.length-1);
-
- } else if (v == btnTimerDraw) {
- oldY = centerY;
- mTimer.schedule(mTimerTask, 0, 5);
- }
-
- }
-
- }
-
- class MyTimerTask extends TimerTask {
- @Override
- public void run() {
-
- SimpleDraw(currentX);
- currentX++;
- if (currentX == Y_axis.length - 1) {
- ClearDraw();
- currentX = 0;
- oldY = centerY;
- }
- }
-
- }
-
-
- void SimpleDraw(int length) {
- if (length == 0)
- oldX = 0;
- Canvas canvas = sfh.lockCanvas(new Rect(oldX, 0, oldX + length,
- getWindowManager().getDefaultDisplay().getHeight()));
- Log.i("Canvas:",
- String.valueOf(oldX) + "," + String.valueOf(oldX + length));
-
- Paint mPaint = new Paint();
- mPaint.setColor(Color.GREEN);
- mPaint.setStrokeWidth(2);
-
- int y;
- for (int i = oldX + 1; i < length; i++) {
- y = Y_axis[i - 1];
- canvas.drawLine(oldX, oldY, i, y, mPaint);
- oldX = i;
- oldY = y;
- }
- sfh.unlockCanvasAndPost(canvas);
- }
-
- void ClearDraw() {
- Canvas canvas = sfh.lockCanvas(null);
- canvas.drawColor(Color.BLACK);
- sfh.unlockCanvasAndPost(canvas);
-
- }
- }
注意一下 for (int i = oldX + 1; i < length; i++) {// 绘画正弦波 这句,在.lockCanvas()指定Rect内减少循环画线的次数,可以提高绘图效率。