android繪制觸點(diǎn)軌跡的代碼
本文實(shí)例為大家分享了android繪制觸點(diǎn)軌跡的具體代碼,供大家參考,具體內(nèi)容如下
重點(diǎn)函數(shù)是onTouchEvent(),所有的觸摸事件都會在View的這個函數(shù)里面處理
單點(diǎn)觸控
單點(diǎn)觸控的event是通過event.getAction()獲得的,一般最少需要考慮下面這三種情況
MotionEvent.ACTION_DOWN:
- 手指 初次接觸到屏幕 時觸發(fā)。
MotionEvent.ACTION_MOVE:
- 手指 在屏幕上滑動 時觸發(fā),會多次觸發(fā)。
MotionEvent.ACTION_UP:
- 手指 離開屏幕 時觸發(fā)。
多點(diǎn)觸控
多點(diǎn)觸控的event是通過event.getActionMasked()獲得的,一般最少需要考慮下面這個五種情況,因?yàn)橛卸鄠€點(diǎn)需要處理,所以需要判斷event是哪一個觸摸點(diǎn)的事件,Android因此導(dǎo)入了比較多的概念,下面通過對關(guān)鍵函數(shù)的解析來說明。
注意:方法的說明中添加了我的注釋,請留意。另外,每一組函數(shù)和這個模塊最后都有我寫的總結(jié)性的文字。
MotionEvent提供了很多看似能直接得到觸摸點(diǎn)的方法,但是,這些方法并不是直接拿來能用的,具體的關(guān)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);//注意返回值表達(dá)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() { //這個表達(dá)式實(shí)際就是說取getAction()函數(shù)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() { //這個表達(dá)式的意思就是說取getAction()函數(shù)的低8位 return nativeGetAction(mNativePtr) & ACTION_MASK; }
總結(jié):這就很簡單明了了,Acton包含兩個部分,高8位表示觸摸點(diǎn)的index,低8位表示具體的事件。
注意這里的觸摸點(diǎn)的index,指的是Action中的,而不是event中的,這是兩個概念。
getPointerId()和findPointerIndex()
getPointerID()
//注意函數(shù)的注釋第一句的說明,表示,返回的id叫pointer identifier,是和event里面的數(shù)據(jù)關(guān)聯(lián)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 individual 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()
//注意函數(shù)的注釋里面第一句,意思是提供一個pointer identifier,返回event中對應(yīng)數(shù)據(jù)的index //index of data的作用是傳給event.getX()等其他的函數(shù)來獲取坐標(biāo)等信息 //所以這個函數(shù)的名字改成getPointerDataIndex比較合適 /** * 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); }
總結(jié):這里引入了兩個概念,一個是pointer identifier,很好理解,就是指針的id,一個是index of its data.
總結(jié)
MotionEvent.getAction返回的是actionIndex和mask的連接體,通過actionIndex可以獲取到對應(yīng)的pointerID,通過pointerID可以獲取到對應(yīng)數(shù)據(jù)包的ID,然后通過getX()來獲取對應(yīng)的數(shù)據(jù)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:
- 多點(diǎn)觸控時按下手指時觸發(fā),如果當(dāng)前只有一個點(diǎn),則不會觸發(fā)此事件。
MotionEvent.ACTION_POINTER_DOWN:
- 多點(diǎn)觸控抬起手指時觸發(fā),如果當(dāng)前只有一個點(diǎn),則不會觸發(fā)此事件。
MotionEvent.ACTION_DOWN:
- 第一個手指按下時觸發(fā)
MotionEvent.ACTION_UP:
- 最后一個手指離開時觸發(fā)
MotionEvent.ACTION_MOVE:
1.所有的手指滑動時觸發(fā)此事件
2.如果有多個點(diǎn),同時移動,需要在ACTION_MOVE里面添加循環(huán)語句。
3.考慮到刷新效率的問題,可以通過event.getHistoricalX()和event.getHistoricalY()來獲取存在緩存中的數(shù)據(jù),后面的例子中有說明
實(shí)例
獲取默認(rèn)屏幕長和寬的代碼
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;
自定義View的代碼
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 = ;//作用僅僅是獲取默認(rèn)屏幕的長和寬 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); } }
以上就是本文的全部內(nèi)容,希望對大家的學(xué)習(xí)有所幫助,也希望大家多多支持腳本之家。
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