android 多点触控Demo

最新推荐文章于 2022-09-28 19:20:14 发布

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本文介绍了一个Android应用中通过多指触摸事件实现的矩形动态缩放功能，用户可以通过滑动两个手指控制矩形大小，增强用户体验。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

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);
    }
 
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		// TODO Auto-generated method stub
		switch(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 stub
		Log.d(TAG, "TouchIndicatorView ---------- init");
		indicatorSize = 80f;
		setTextColor(Color.BLACK);
		setTextSize(30f);
		setText(indicatorText);
		setGravity(Gravity.CENTER_HORIZONTAL);
	}

	@Override
	protected void onDraw(Canvas canvas) {
		// TODO Auto-generated method stub
		super.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>