android 多点触控Demo

代码功能：

View上绘制一个矩形，实现两个手指在屏幕上滑动，当两个手指直接的距离增大时，矩形放大，反之矩形缩小。

代码如下：

1.TouchDemoActivity.java

package com.camera.touchdemo;import android.app.Activity;import android.os.Bundle;import android.util.FloatMath;import android.util.Log;import android.view.MotionEvent;public class TouchDemoActivity extends Activity {private static final String TAG = "lxy";private boolean isZoom;private TouchIndicatorView touchIndicatorView;private float oldSpace;private float newSpace;private boolean newBigThanOldSpace; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); touchIndicatorView = (TouchIndicatorView) findViewById(R.id.touch_indicator_view); } @Overridepublic boolean onTouchEvent(MotionEvent event) {// TODO Auto-generated method stubswitch(event.getActionMasked()){case MotionEvent.ACTION_DOWN:Log.d(TAG, "onTouchEvent__________ action down");break; case MotionEvent.ACTION_POINTER_UP: isZoom = false; Log.d(TAG, "onTouchEvent__________ action pointer up"); break; /** * API原文是 A non-primary pointer has gone down. * 翻译过来就是：非第一个点按下 */ case MotionEvent.ACTION_POINTER_DOWN: isZoom = true; Log.d(TAG, "onTouchEvent__________ action pointer down"); break; case MotionEvent.ACTION_MOVE: if(isZoom){ newSpace = spacing(event); newBigThanOldSpace = newSpace > oldSpace ? true : false; touchIndicatorView.addShowIndicatorSize(newBigThanOldSpace); oldSpace = newSpace; Log.d(TAG, "onTouchEvent__________ action move : space = " + spacing(event)); } break;default:break;}//return super.onTouchEvent(event);return true;}private float spacing(MotionEvent event) { float x = event.getX(0) - event.getX(1); float y = event.getY(0) - event.getY(1); return FloatMath.sqrt(x * x + y * y); } }

2.TouchIndicatorView.java

package com.camera.touchdemo;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.util.AttributeSet;import android.util.Log;import android.view.Gravity;import android.widget.TextView;public class TouchIndicatorView extends TextView{private static final String TAG = "lxy";private static final float CX = 240f;private static final float CY = 300f;private Paint mPaint;private float indicatorSize;private String indicatorText = "1.0X";public TouchIndicatorView(Context context, AttributeSet attrs) {super(context, attrs);// TODO Auto-generated constructor stubLog.d(TAG, "TouchIndicatorView ---------- init");indicatorSize = 80f;setTextColor(Color.BLACK);setTextSize(30f);setText(indicatorText);setGravity(Gravity.CENTER_HORIZONTAL);}@Overrideprotected void onDraw(Canvas canvas) {// TODO Auto-generated method stubsuper.onDraw(canvas);if(mPaint == null){mPaint = new Paint();}mPaint.setColor(Color.BLACK);float []points = {CX-indicatorSize, CY-indicatorSize /*A*/ , CX+indicatorSize, CY-indicatorSize /*B*/ ,CX-indicatorSize, CY+indicatorSize /*C*/ , CX+indicatorSize, CY+indicatorSize /*D*/ ,CX-indicatorSize, CY-indicatorSize /*A*/ , CX-indicatorSize, CY+indicatorSize /*C*/ ,CX+indicatorSize, CY-indicatorSize /*B*/ , CX+indicatorSize, CY+indicatorSize /*D*/ ,};canvas.drawLines(points, 0, 16, mPaint); //mPaint.setTextSize(30);canvas.drawText(indicatorText, CX-15, CY+indicatorSize+15, mPaint);}public void addShowIndicatorSize(boolean addShowSize){if(addShowSize){if(indicatorSize > 180 ){indicatorText = "4.0X";setText(indicatorText);return;}indicatorSize ++;}else{if(indicatorSize < 80 ){indicatorText = "1.0X";setText(indicatorText);return;}indicatorSize --;}float forSizeText = (indicatorSize-80)/33 + 1 ;forSizeText = forSizeText > 4 ? 4 : forSizeText;forSizeText = forSizeText < 1 ? 1 : forSizeText;indicatorText = String.valueOf(forSizeText).substring(0, 3) + "X";setText(indicatorText);invalidate();}}

3.main.xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <com.camera.touchdemo.TouchIndicatorView android:id="@+id/touch_indicator_view" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="#FFFFFFFF" ></com.camera.touchdemo.TouchIndicatorView></LinearLayout>

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