Android编程开发之多点触摸(Multitouch)实现方法

本文实例讲述了Android编程开发之多点触摸(Multitouch)实现方法。分享给大家供大家参考，具体如下：

如果您对开发多点触摸程序感兴趣的话，那么本文将是一个很好的开始，android应用程序开发中，多点触摸不是那么遥不可及，实现起来也很简单，本例只需要两个类就能实现多点触摸。

首先来看看我们的视图类MTView.java:

package com.ideasandroid.demo;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class MTView extends SurfaceView implements SurfaceHolder.Callback {
  private static final int MAX_TOUCHPOINTS = 10;
  private static final String START_TEXT = "请随便触摸屏幕进行测试";
  private Paint textPaint = new Paint();
  private Paint touchPaints[] = new Paint[MAX_TOUCHPOINTS];
  private int colors[] = new int[MAX_TOUCHPOINTS];
  private int width, height;
  private float scale = 1.0f;
  public MTView(Context context) {
    super(context);
    SurfaceHolder holder = getHolder();
    holder.addCallback(this);
    setFocusable(true); // 确保我们的View能获得输入焦点
    setFocusableInTouchMode(true); // 确保能接收到触屏事件
    init();
  }
  private void init() {
    // 初始化10个不同颜色的画笔
    textPaint.setColor(Color.WHITE);
    colors[0] = Color.BLUE;
    colors[1] = Color.RED;
    colors[2] = Color.GREEN;
    colors[3] = Color.YELLOW;
    colors[4] = Color.CYAN;
    colors[5] = Color.MAGENTA;
    colors[6] = Color.DKGRAY;
    colors[7] = Color.WHITE;
    colors[8] = Color.LTGRAY;
    colors[9] = Color.GRAY;
    for (int i = 0; i < MAX_TOUCHPOINTS; i++) {
      touchPaints[i] = new Paint();
      touchPaints[i].setColor(colors[i]);
    }
  }
  /*
   * 处理触屏事件
   */
  @Override
  public boolean onTouchEvent(MotionEvent event) {
    // 获得屏幕触点数量
    int pointerCount = event.getPointerCount();
    if (pointerCount > MAX_TOUCHPOINTS) {
      pointerCount = MAX_TOUCHPOINTS;
    }
    // 锁定Canvas,开始进行相应的界面处理
    Canvas c = getHolder().lockCanvas();
    if (c != null) {
      c.drawColor(Color.BLACK);
      if (event.getAction() == MotionEvent.ACTION_UP) {
        // 当手离开屏幕时，清屏
      } else {
        // 先在屏幕上画一个十字，然后画一个圆
        for (int i = 0; i < pointerCount; i++) {
          // 获取一个触点的坐标，然后开始绘制
          int id = event.getPointerId(i);
          int x = (int) event.getX(i);
          int y = (int) event.getY(i);
          drawCrosshairsAndText(x, y, touchPaints[id], i, id, c);
        }
        for (int i = 0; i < pointerCount; i++) {
          int id = event.getPointerId(i);
          int x = (int) event.getX(i);
          int y = (int) event.getY(i);
          drawCircle(x, y, touchPaints[id], c);
        }
      }
      // 画完后，unlock
      getHolder().unlockCanvasAndPost(c);
    }
    return true;
  }
  /**
   * 画十字及坐标信息
   *
   * @param x
   * @param y
   * @param paint
   * @param ptr
   * @param id
   * @param c
   */
  private void drawCrosshairsAndText(int x, int y, Paint paint, int ptr,
      int id, Canvas c) {
    c.drawLine(0, y, width, y, paint);
    c.drawLine(x, 0, x, height, paint);
    int textY = (int) ((15 + 20 * ptr) * scale);
    c.drawText("x" + ptr + "=" + x, 10 * scale, textY, textPaint);
    c.drawText("y" + ptr + "=" + y, 70 * scale, textY, textPaint);
    c.drawText("id" + ptr + "=" + id, width - 55 * scale, textY, textPaint);
  }
  /**
   * 画圆
   *
   * @param x
   * @param y
   * @param paint
   * @param c
   */
  private void drawCircle(int x, int y, Paint paint, Canvas c) {
    c.drawCircle(x, y, 40 * scale, paint);
  }
  /*
   * 进入程序时背景画成黑色，然后把“START_TEXT”写到屏幕
   */
  public void surfaceChanged(SurfaceHolder holder, int format, int width,
      int height) {
    this.width = width;
    this.height = height;
    if (width > height) {
      this.scale = width / 480f;
    } else {
      this.scale = height / 480f;
    }
    textPaint.setTextSize(14 * scale);
    Canvas c = getHolder().lockCanvas();
    if (c != null) {
      // 背景黑色
      c.drawColor(Color.BLACK);
      float tWidth = textPaint.measureText(START_TEXT);
      c.drawText(START_TEXT, width / 2 - tWidth / 2, height / 2,
          textPaint);
      getHolder().unlockCanvasAndPost(c);
    }
  }
  public void surfaceCreated(SurfaceHolder holder) {
  }
  public void surfaceDestroyed(SurfaceHolder holder) {
  }
}

代码中都做了相应的注释，这里就不多说。

接下来看看我们的Activity，MultitouchVisible.java

package com.ideasandroid.demo;
import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;
public class MultitouchVisible extends Activity {
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //隐藏标题栏
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    //设置成全屏
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
        WindowManager.LayoutParams.FLAG_FULLSCREEN);
    //设置为上面的MTView
    setContentView(new MTView(this));
  }
}

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希望本文所述对大家Android程序设计有所帮助。