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); } @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>