編輯:關於Android編程
Gesture在 ViewGroup中使用
GestureDetector類可以讓我們快速的處理手勢事件,如點擊,滑動等。
使用GestureDetector分三步:
1. 定義GestureDetector類
2. 初始化手勢類,同時設置手勢監聽
3. 將touch事件交給gesture處理
先來了解一下如何使用,後面會有示例:
package com.example.y2222.myview; import android.content.Context; import android.util.AttributeSet; import android.util.Log; import android.view.GestureDetector; import android.view.MotionEvent; import android.widget.LinearLayout; /** * Created by raise.yang on 2016/06/29. */ public class GestureDemoView extends LinearLayout { //1,定義GestureDetector類 private GestureDetector m_gestureDetector; public GestureDemoView(Context context, AttributeSet attrs) { this(context, attrs, 0); } public GestureDemoView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); //設置為可點擊 setClickable(true); //2,初始化手勢類,同時設置手勢監聽 m_gestureDetector = new GestureDetector(context, onGestureListener); //雙擊監聽-一般很少用到 m_gestureDetector.setOnDoubleTapListener(onDoubleTapListener); } @Override public boolean onTouchEvent(MotionEvent event) { //3,將touch事件交給gesture處理 m_gestureDetector.onTouchEvent(event); return super.onTouchEvent(event); } //初始化手勢監聽對象,使用GestureDetector.OnGestureListener的實現抽象類,因為實際開發中好多方法用不上 private final GestureDetector.OnGestureListener onGestureListener = new GestureDetector.SimpleOnGestureListener() { @Override public boolean onSingleTapUp(MotionEvent e) { Log.d("GestureDemoView", "onSingleTapUp() "); return super.onSingleTapUp(e); } @Override public void onLongPress(MotionEvent e) { Log.d("GestureDemoView", "onLongPress() "); super.onLongPress(e); } @Override public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) { Log.d("GestureDemoView", "onScroll() distanceX = " + distanceX); return super.onScroll(e1, e2, distanceX, distanceY); } @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { Log.d("GestureDemoView", "onFling() velocityX = " + velocityX); return super.onFling(e1, e2, velocityX, velocityY); } @Override public void onShowPress(MotionEvent e) { Log.d("GestureDemoView", "onShowPress() "); super.onShowPress(e); } @Override public boolean onDown(MotionEvent e) { Log.d("GestureDemoView", "onDown() "); return super.onDown(e); } @Override public boolean onDoubleTap(MotionEvent e) { Log.d("GestureDemoView", "onDoubleTap() "); return super.onDoubleTap(e); } @Override public boolean onDoubleTapEvent(MotionEvent e) { Log.d("GestureDemoView", "onDoubleTapEvent() "); return super.onDoubleTapEvent(e); } @Override public boolean onSingleTapConfirmed(MotionEvent e) { Log.d("GestureDemoView", "onSingleTapConfirmed() "); return super.onSingleTapConfirmed(e); } @Override public boolean onContextClick(MotionEvent e) { Log.d("GestureDemoView", "onContextClick() "); return super.onContextClick(e); } }; private final GestureDetector.OnDoubleTapListener onDoubleTapListener = new GestureDetector.OnDoubleTapListener() { @Override public boolean onSingleTapConfirmed(MotionEvent e) { Log.d("GestureDemoView", "onSingleTapConfirmed() OnDoubleTapListener"); return false; } @Override public boolean onDoubleTap(MotionEvent e) { Log.d("GestureDemoView", "onDoubleTap() OnDoubleTapListener"); return false; } @Override public boolean onDoubleTapEvent(MotionEvent e) { Log.d("GestureDemoView", "onDoubleTapEvent() OnDoubleTapListener"); return false; } }; }
注意:setClickable(true);一定要加,不然只會收到下例3個事件,被這個整了好長時間才找到原因.(⊙﹏⊙)b
對於單擊,雙擊,拖動等事件調用見下圖:
根據上圖,每個方法大致都調用了,說明幾個容易弄混的回調方法
1. onScroll()
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY)
e1:滑動事件的起點(也就是說onDown()的時候)
e2:當前滑動位置點(手指的位置)
distanceX:上次滑動(調用onScroll)到這次滑動的X軸的距離px,不是e1點到e2點的X軸的距離
distanceY:上次滑動(調用onScroll)到這次滑動的Y軸的距離px,不是e1點到e2點的Y軸的距離
2. onFling()
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)
e1:拖動動事件的起點(也就是說onDown()的時候)
e2:onFling()調用時,手指的位置
velocityX:X軸上每秒滑動像素值
velocityY:Y軸上每秒滑動像素值
注意:當拖動速率velocityX或velocityY超過ViewConfiguration.getMinimumFlingVelocity()最小拖動速率時,才會調用onFling(),也就是如果只拖動一點,或是慢慢的拖動,是不會觸發該方法。
對應源碼:
if ((Math.abs(velocityY) > mMinimumFlingVelocity) || (Math.abs(velocityX) > mMinimumFlingVelocity)){ handled = mListener.onFling(mCurrentDownEvent, ev, velocityX, velocityY); }
實踐:使用GestureDetector實現左滑刪除
在很多ListView中都有該效果,現在自己實現下,順便熟悉GestureDetector的使用。
效果圖:
GestureDemoView.java:
package com.example.y2222.myview; import android.content.Context; import android.util.AttributeSet; import android.util.Log; import android.view.GestureDetector; import android.view.LayoutInflater; import android.view.MotionEvent; import android.widget.LinearLayout; import com.example.y2222.myapplication.R; /** * Created by raise.yang on 2016/06/29. */ public class GestureDemoView extends LinearLayout { //1,定義GestureDetector類 private GestureDetector m_gestureDetector; private int m_max_scrollX; public GestureDemoView(Context context, AttributeSet attrs) { this(context, attrs, 0); } public GestureDemoView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); //設置為可點擊 setClickable(true); //2,初始化手勢類,同時設置手勢監聽 m_gestureDetector = new GestureDetector(context, onGestureListener); LayoutInflater.from(context).inflate(R.layout.view_gesture, this); } @Override public boolean onTouchEvent(MotionEvent event) { //3,將touch事件交給gesture處理 m_gestureDetector.onTouchEvent(event); if (event.getAction() == MotionEvent.ACTION_UP) { // GestureDetector沒有處理up事件的方法,只能在這裡處理了。 int scrollX = getScrollX(); if (scrollX > m_max_scrollX / 2) { show_right_view(); } else { hide_right_view(); } } return super.onTouchEvent(event); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); int childCount = getChildCount(); for (int i = 0; i < childCount; i++) { //測量子view的寬高,?不測量,右側布局會不顯示,這裡有點疑問 measureChild(getChildAt(i), widthMeasureSpec, heightMeasureSpec); if (i == 1) { m_max_scrollX = getChildAt(i).getMeasuredWidth(); } } } //初始化手勢監聽對象,使用GestureDetector.OnGestureListener的實現抽象類,因為實際開發中好多方法用不上 private final GestureDetector.OnGestureListener onGestureListener = new GestureDetector.SimpleOnGestureListener() { @Override public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) { Log.d("GestureDemoView", "onScroll() distanceX = " + distanceX + " getScrollX = " + getScrollX() + " max_scrollX = " + m_max_scrollX); int scrollX = getScrollX(); int minScrollX = -scrollX; int maxScrollY = m_max_scrollX - scrollX; // 對滑動的距離邊界控制 if (distanceX > maxScrollY) { distanceX = maxScrollY; } else if (distanceX < minScrollX) { distanceX = minScrollX; } scrollBy((int) distanceX, 0); return true; } @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { Log.d("GestureDemoView", "onFling() velocityX = " + velocityX); if (velocityX < 0) { //快速向左滑動 show_right_view(); } else { hide_right_view(); } return super.onFling(e1, e2, velocityX, velocityY); } }; private void show_right_view() { scrollTo(m_max_scrollX, 0); } private void hide_right_view() { scrollTo(0, 0); } }
view_gesture.xml
<?xml version="1.0" encoding="utf-8"?> <merge xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal"> <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center" android:text="左側布局"/> <LinearLayout android:layout_width="wrap_content" android:layout_height="match_parent" android:orientation="horizontal" > <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="收藏"/> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="刪除"/> </LinearLayout> </merge>
xml文件中根標簽使用<merge>,可減少一層view樹嵌套,並且使用getChildCount()能得到我們想要的子view個數。
關於<merge>標簽的使用,詳見郭神的blog:http://blog.csdn.net/guolin_blog/article/details/43376527
實現也很簡單,在scroll和fling的時候,得到滑動距離或滑動速度,再調用view自己的scrollTo()或scrollBy()滑動內部元素即可。
從效果圖中,當滑動到一半松手時,立即滑動到最左邊,完全沒有動畫,這樣的體驗很差,所以還需優化。關於滑動時增加動畫效果,可以使用Scroller類完成,准備下期補上。
Gesture在 View中使用
和在viewgroup中一樣,在view中,同樣是經過三步來實現:
1. 定義GestureDetector類
2. 初始化手勢類,同時設置手勢監聽
3. 將touch事件交給gesture處理
舉個荔枝:
做了一個小球跟隨手指移動的效果,先繪制小球,當手指放在小球上滑動時,會調用onScroll(),在這個方法中,修改圓心的位置進行重繪,這樣小球就能移動了。
這裡有2個難點:
1. 如何判斷手指落在了小球上;
2. 滑動到邊界時,不能超過邊界;
效果圖:
GestureView.java代碼:
package com.example.y2222.myview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Paint; import android.util.AttributeSet; import android.view.GestureDetector; import android.view.MotionEvent; import android.view.View; /** * Created by raise.yang on 2016/07/05. */ public class GestureView extends View { private GestureDetector m_gestureDetector; private Paint m_paint; //小球的中心點 private float centerX; private float centerY; //小球的半徑 private int radius; //是否touch在小球上 private boolean touch_bool; public GestureView(Context context, AttributeSet attrs) { this(context, attrs, 0); } public GestureView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); // 初始畫筆 m_paint = new Paint(Paint.ANTI_ALIAS_FLAG); m_paint.setColor(getResources().getColor(android.R.color.holo_blue_light)); //設置為可點擊 setClickable(true); //2,初始化手勢類,同時設置手勢監聽 m_gestureDetector = new GestureDetector(context, onGestureListener); radius = 50; } @Override public boolean onTouchEvent(MotionEvent event) { //3,將touch事件交給gesture處理 m_gestureDetector.onTouchEvent(event); if (event.getAction() == MotionEvent.ACTION_DOWN) { //判斷手指落在了小球上 if (getDistanceByPoint((int) centerX, (int) centerY, (int) event.getX(), (int) event.getY()) < radius) { touch_bool = true; } else { touch_bool = false; } } return super.onTouchEvent(event); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { // 默認圓心在中心點 if (w > 0) { centerX = w / 2; } if (h > 0) { centerY = h / 2; } } @Override protected void onDraw(Canvas canvas) { canvas.drawCircle(centerX, centerY, radius, m_paint); } GestureDetector.OnGestureListener onGestureListener = new GestureDetector.SimpleOnGestureListener() { @Override public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) { if (touch_bool) { centerY -= distanceY; centerX -= distanceX; //處理邊界問題 if (centerX < radius) { centerX = radius; } else if (centerX > getWidth() - radius) { centerX = getWidth() - radius; } if (centerY < radius) { centerY = radius; } else if (centerY > getHeight() - radius) { centerY = getHeight() - radius; } //修改圓心後,通知重繪 postInvalidate(); } return true; } }; /** * 計算兩點間的距離 */ private int getDistanceByPoint(int x1, int y1, int x2, int y2) { double temp = Math.abs((x2 - x1) * (x2 - x1) - (y2 - y1) * (y2 - y1)); return (int) Math.sqrt(temp); } }
在處理問題1時,我設置了一個boolean值,在用戶觸摸的時候去判斷,當前點和圓心點的距離是否小於半徑,若小於,說明在圓內。這樣在滑動的時候,就去判斷一下,是否需要滑動小球。
控制邊界,其實就是控制圓心點的坐標,只要保證落在(radius,radius),(getWidth()-radius,getHeight()-radius)兩點矩形中即可。
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