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SurfaceView的基本使用

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  • Post category:其他




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：












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:



  2. <linearlayout xmlns:android=”http://schemas.android.com/apk/res/android”

  3. android:layout_width=”fill_parent” android:layout_height=”fill_parent”

  4. android:orientation=”vertical”>


  6. <linearlayout android:id=”@+id/LinearLayout01″

  7. android:layout_width=”wrap_content” android:layout_height=”wrap_content”>

  8. <button android:id=”@+id/Button01″ android:layout_width=”wrap_content”

  9. android:layout_height=”wrap_content” android:text=”简单绘画”>

  10. <button android:id=”@+id/Button02″ android:layout_width=”wrap_content”

  11. android:layout_height=”wrap_content” android:text=”定时器绘画”>


  13. <surfaceview android:id=”@+id/SurfaceView01″

  14. android:layout_width=”fill_parent” android:layout_height=”fill_parent”>



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接下来贴出程序源码：





  1. package com.testSurfaceView;


  3. import java.util.Timer;

  4. import java.util.TimerTask;


  6. import android.app.Activity;

  7. import android.graphics.Canvas;

  8. import android.graphics.Color;

  9. import android.graphics.Paint;

  10. import android.graphics.Rect;

  11. import android.os.Bundle;

  12. import android.util.Log;

  13. import android.view.SurfaceHolder;

  14. import android.view.SurfaceView;

  15. import android.view.View;

  16. import android.widget.Button;


  18. public class testSurfaceView extends Activity {


  19. /** Called when the activity is first created. */

  20. Button btnSimpleDraw, btnTimerDraw;

  21. SurfaceView sfv;

  22. SurfaceHolder sfh;


  24. private Timer mTimer;

  25. private MyTimerTask mTimerTask;

  26. int Y_axis[],//保存正弦波的Y轴上的点

  27. centerY,//中心线

  28. oldX,oldY,//上一个XY点

  29. currentX;//当前绘制到的X轴上的点


  31. @Override

  32. public void onCreate(Bundle savedInstanceState) {


  33. super.onCreate(savedInstanceState);

  34. setContentView(R.layout.main);


  36. btnSimpleDraw = (Button) this.findViewById(R.id.Button01);

  37. btnTimerDraw = (Button) this.findViewById(R.id.Button02);

  38. btnSimpleDraw.setOnClickListener(new ClickEvent());

  39. btnTimerDraw.setOnClickListener(new ClickEvent());

  40. sfv = (SurfaceView) this.findViewById(R.id.SurfaceView01);

  41. sfh = sfv.getHolder();


  43. //动态绘制正弦波的定时器

  44. mTimer = new Timer();

  45. mTimerTask = new MyTimerTask();


  47. // 初始化y轴数据

  48. centerY = (getWindowManager().getDefaultDisplay().getHeight() – sfv

  49. .getTop()) / 2;

  50. Y_axis = new int[getWindowManager().getDefaultDisplay().getWidth()];

  51. for (int i = 1; i < Y_axis.length; i++) {// 计算正弦波

  52. Y_axis[i – 1] = centerY

  53. – (int) (100 * Math.sin(i * 2 * Math.PI / 180));

  54. }

  55. }


  57. class ClickEvent implements View.OnClickListener {



  59. @Override

  60. public void onClick(View v) {



  62. if (v == btnSimpleDraw) {


  63. SimpleDraw(Y_axis.length-1);//直接绘制正弦波


  65. } else if (v == btnTimerDraw) {


  66. oldY = centerY;

  67. mTimer.schedule(mTimerTask, 0, 5);//动态绘制正弦波

  68. }


  70. }


  72. }


  74. class MyTimerTask extends TimerTask {


  75. @Override

  76. public void run() {



  78. SimpleDraw(currentX);

  79. currentX++;//往前进

  80. if (currentX == Y_axis.length – 1) {//如果到了终点，则清屏重来

  81. ClearDraw();

  82. currentX = 0;

  83. oldY = centerY;

  84. }

  85. }


  87. }


  89. /*

  90. * 绘制指定区域

  91. */

  92. void SimpleDraw(int length) {


  93. if (length == 0)

  94. oldX = 0;

  95. Canvas canvas = sfh.lockCanvas(new Rect(oldX, 0, oldX + length,

  96. getWindowManager().getDefaultDisplay().getHeight()));// 关键:获取画布

  97. Log.i(“Canvas:”,

  98. String.valueOf(oldX) + “,” + String.valueOf(oldX + length));


  100. Paint mPaint = new Paint();

  101. mPaint.setColor(Color.GREEN);// 画笔为绿色

  102. mPaint.setStrokeWidth(2);// 设置画笔粗细


  104. int y;

  105. for (int i = oldX + 1; i < length; i++) {// 绘画正弦波

  106. y = Y_axis[i – 1];

  107. canvas.drawLine(oldX, oldY, i, y, mPaint);

  108. oldX = i;

  109. oldY = y;

  110. }

  111. sfh.unlockCanvasAndPost(canvas);// 解锁画布，提交画好的图像

  112. }


  114. void ClearDraw() {


  115. Canvas canvas = sfh.lockCanvas(null);

  116. canvas.drawColor(Color.BLACK);// 清除画布

  117. sfh.unlockCanvasAndPost(canvas);


  119. }

  120. }


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