本文实例为大家分享了android绘制触点轨迹的具体代码，供大家参考，具体内容如下
重点函数是onTouchEvent()，所有的触摸事件都会在View的这个函数里面处理
单点触控
单点触控的event是通过event.getAction()获得的，一般最少需要考虑下面这三种情况
MotionEvent.ACTION_DOWN:
手指 初次接触到屏幕 时触发。
MotionEvent.ACTION_MOVE:
手指 在屏幕上滑动 时触发，会多次触发。
MotionEvent.ACTION_UP:
手指 离开屏幕 时触发。
多点触控
多点触控的event是通过event.getActionMasked()获得的，一般最少需要考虑下面这个五种情况，因为有多个点需要处理，所以需要判断event是哪一个触摸点的事件，Android因此导入了比较多的概念，下面通过对关键函数的解析来说明。
注意：方法的说明中添加了我的注释，请留意。另外，每一组函数和这个模块最后都有我写的总结性的文字。
MotionEvent提供了很多看似能直接得到触摸点的方法，但是，这些方法并不是直接拿来能用的，具体的关系如下
getAction()和getActionIndex()以及getActionMasked()
getAction()
/** * Return the kind of action being performed. * Consider using {@link #getActionMasked} and {@link #getActionIndex} to retrieve * the separate masked action and pointer index. * @return The action, such as {@link #ACTION_DOWN} or * the combination of {@link #ACTION_POINTER_DOWN} with a shifted pointer index. */ public final int getAction() { return nativeGetAction(mNativePtr);//注意返回值表达式 }
getActionIndex()
public static final int ACTION_POINTER_INDEX_MASK = 0xff00; public static final int ACTION_POINTER_INDEX_SHIFT = 8; /** * For {@link #ACTION_POINTER_DOWN} or {@link #ACTION_POINTER_UP} * as returned by {@link #getActionMasked}, this returns the associated * pointer index. * The index may be used with {@link #getPointerId(int)}, * {@link #getX(int)}, {@link #getY(int)}, {@link #getPressure(int)}, * and {@link #getSize(int)} to get information about the pointer that has * gone down or up. * @return The index associated with the action. */ public final int getActionIndex() { //这个表达式实际就是说取getAction()函数返回值的高8位 return (nativeGetAction(mNativePtr) & ACTION_POINTER_INDEX_MASK) >> ACTION_POINTER_INDEX_SHIFT; }
getActionMasked()
public static final int ACTION_MASK = 0xff; /** * Return the masked action being performed, without pointer index information. * Use {@link #getActionIndex} to return the index associated with pointer actions. * @return The action, such as {@link #ACTION_DOWN} or {@link #ACTION_POINTER_DOWN}. */ public final int getActionMasked() { //这个表达式的意思就是说取getAction()函数的低8位 return nativeGetAction(mNativePtr) & ACTION_MASK; }
总结：这就很简单明了了，Acton包含两个部分，高8位表示触摸点的index，低8位表示具体的事件。注意这里的触摸点的index，指的是Action中的，而不是event中的，这是两个概念。
getPointerId()和findPointerIndex()
getPointerID()
//注意函数的注释第一句的说明，表示，返回的id叫pointer identifier,是和event里面的数据关联的 /** * Return the pointer identifier associated with a particular pointer * data index in this event. The identifier tells you the actual pointer * number associated with the data, accounting for inpidual pointers * going up and down since the start of the current gesture. * @param pointerIndex Raw index of pointer to retrieve. Value may be from 0 * (the first pointer that is down) to {@link #getPointerCount()}-1. */ public final int getPointerId(int pointerIndex) { return nativeGetPointerId(mNativePtr, pointerIndex); }
findPointerIndex()
//注意函数的注释里面第一句，意思是提供一个pointer identifier,返回event中对应数据的index //index of data的作用是传给event.getX()等其他的函数来获取坐标等信息 //所以这个函数的名字改成getPointerDataIndex比较合适 /** * Given a pointer identifier, find the index of its data in the event. * * @param pointerId The identifier of the pointer to be found. * @return Returns either the index of the pointer (for use with * {@link #getX(int)} et al.), or -1 if there is no data available for * that pointer identifier. */ public final int findPointerIndex(int pointerId) { return nativeFindPointerIndex(mNativePtr, pointerId); }
总结：这里引入了两个概念，一个是pointer identifier,很好理解，就是指针的id,一个是index of its data.
总结
MotionEvent.getAction返回的是actionIndex和mask的连接体，通过actionIndex可以获取到对应的pointerID,通过pointerID可以获取到对应数据包的ID，然后通过getX()来获取对应的数据信息
基本的使用方法示例
int index = event.getActionIndex();int id = event.getPointerId(index);int pointerIndex = event.findPointerIndex(id);int x=getX(pointerIndex);int y=getY(pointerIndex);
MotionEvent.ACTION_POINTER_DOWN:
多点触控时按下手指时触发，如果当前只有一个点，则不会触发此事件。
MotionEvent.ACTION_POINTER_DOWN:
多点触控抬起手指时触发，如果当前只有一个点，则不会触发此事件。
MotionEvent.ACTION_DOWN:
第一个手指按下时触发
MotionEvent.ACTION_UP:
最后一个手指离开时触发
MotionEvent.ACTION_MOVE:
1.所有的手指滑动时触发此事件2.如果有多个点，同时移动，需要在ACTION_MOVE里面添加循环语句。3.考虑到刷新效率的问题，可以通过event.getHistoricalX()和event.getHistoricalY()来获取存在缓存中的数据，后面的例子中有说明
实例
获取默认屏幕长和宽的代码
WindowManager manager=(WindowManager) getApplicationContext().getSystemService(Context.WINDOW_SERVICE);DisplayMetrics displayMetrics=new DisplayMetrics();Display display=manager.getDefaultDisplay();display.getMetrics(displayMetrics);screenW=displayMetrics.widthPixels;screenH=displayMetrics.heightPixels;
自定义View的代码
import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.PorterDuff;import android.graphics.PorterDuffXfermode;import android.util.AttributeSet;import android.util.Log;import android.view.MotionEvent;import android.view.View;import java.util.HashMap;import java.util.Map;public class TouchTraceView extends View{ Context mContext; private Paint line_paint, text_paint, countPaint; int screenW, screenH; FactoryApplication app; private int paintColor = Color.RED; Map<Integer, TouchPoint> pointMap; float back_x1, back_y1, back_x2, back_y2; public TouchTraceView(Context context, AttributeSet attr) { super(context, attr); mContext = context; app = ;//作用仅仅是获取默认屏幕的长和宽 this.screenH = app.screenH; this.screenW = app.screenW; pointMap = new HashMap<>(); initPaint(); } private void initPaint() { line_paint = new Paint(); line_paint.setAntiAlias(true); line_paint.setColor(paintColor); text_paint = new Paint(); text_paint.setAntiAlias(true); text_paint.setColor(Color.BLUE); text_paint.setTextSize(30); countPaint = new Paint(); countPaint.setAntiAlias(true); countPaint.setColor(Color.GREEN); countPaint.setTextSize(60); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); int num = pointMap.size(); if (num == 0) { clearDraw(canvas); return; } for (Map.Entry<Integer, TouchPoint> entry : pointMap.entrySet()) { TouchPoint point = entry.getValue(); canvas.drawLine(0, point.y, getWidth(), point.y, line_paint); canvas.drawLine(point.x, 0, point.x, getHeight(), line_paint); if (num == 1) { canvas.drawText(" (" + point.x + "," + point.y + ")", screenW / 2, screenH / 2, text_paint); } else { canvas.drawText(String.valueOf(pointMap.size()), screenW / 2, screenH / 2, countPaint); } } } @Override public boolean onTouchEvent(MotionEvent event) { int index = event.getActionIndex(); int id = event.getPointerId(index); int pointerIndex = event.findPointerIndex(id); int pointerCount = event.getPointerCount(); int historySize = event.getHistorySize(); switch (event.getActionMasked()) { case MotionEvent.ACTION_POINTER_DOWN: pointMap.put(pointerIndex, new TouchPoint(event.getX(pointerIndex), event.getY(pointerIndex))); break; case MotionEvent.ACTION_POINTER_UP: pointMap.remove(pointerIndex); break; case MotionEvent.ACTION_MOVE: for (int h = 0; h < historySize; h++) { for (int p = 0; p < pointerCount; p++) { pointMap.put(p, new TouchPoint(event.getHistoricalX(p, h), event.getHistoricalY(p, h))); } } for (int p = 0; p < pointerCount; p++) { pointMap.put(p, new TouchPoint(event.getX(p), event.getY(p))); } break; case MotionEvent.ACTION_DOWN: pointMap.put(0, new TouchPoint(event.getX(pointerIndex), event.getY(pointerIndex))); back_x1 = event.getX(); back_y1 = event.getY(); break; case MotionEvent.ACTION_UP: back_x2 = event.getX(); back_y2 = event.getY(); if (Math.abs(back_x1 - back_x2) > screenW / 2 && Math.abs(back_y1 - back_y2) > screenH / 2) { callOnClick(); } pointMap.clear(); break; default: break; } if (event.getPointerCount() == 0) pointMap.clear(); invalidate(); return true; } class TouchPoint { public float x = 0; public float y = 0; TouchPoint(float x, float y) { this.x = x; this.y = y; } } void clearDraw(Canvas canvas) { Paint paint = new Paint(); paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR)); canvas.drawPaint(paint); paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC)); canvas.drawColor(Color.WHITE); }}
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本文标题: android绘制触点轨迹的代码
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