当我为我的应用程序实现触摸事件时，我遇到了崩溃。我想为我的应用程序实现滑动功能。这是我的代码：
Guetures实现：
package com.example.EventsView;
import android.app.Activity;
import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.MotionEvent;
public class GuesterFilter extends SimpleOnGestureListener{
public final static int SWIPE_UP = 1;
public final static int SWIPE_DOWN = 2;
public final static int SWIPE_LEFT = 3;
public final static int SWIPE_RIGHT = 4;
public final static int MODE_TRANSPARENT = 0;
public final static int MODE_SOLID = 1;
public final static int MODE_DYNAMIC = 2;
private final static int ACTION_FAKE = -13; //just an unlikely number
private int swipe_Min_Distance = 100;
private int swipe_Max_Distance = 350;
private int swipe_Min_Velocity = 100;
private int mode = MODE_DYNAMIC;
private boolean running = true;
private boolean tapIndicator = false;
private Activity context;
private GestureDetector detector;
private SimpleGestureListener listener;
public GuesterFilter(Activity context,SimpleGestureListener sgl) {
this.context = context;
this.detector = new GestureDetector(context, this);
this.listener = sgl;
}
public void onTouchEvent(MotionEvent event){
if(!this.running)
return;
boolean result = this.detector.onTouchEvent(event);
if(this.mode == MODE_SOLID)
event.setAction(MotionEvent.ACTION_CANCEL);
else if (this.mode == MODE_DYNAMIC) {
if(event.getAction() == ACTION_FAKE)
event.setAction(MotionEvent.ACTION_UP);
else if (result)
event.setAction(MotionEvent.ACTION_CANCEL);
else if(this.tapIndicator){
event.setAction(MotionEvent.ACTION_DOWN);
this.tapIndicator = false;
}
}
//else just do nothing, it's Transparent
}
public void setMode(int m){
this.mode = m;
}
public int getMode(){
return this.mode;
}
public void setEnabled(boolean status){
this.running = status;
}
public void setSwipeMaxDistance(int distance){
this.swipe_Max_Distance = distance;
}
public void setSwipeMinDistance(int distance){
this.swipe_Min_Distance = distance;
}
public void setSwipeMinVelocity(int distance){
this.swipe_Min_Velocity = distance;
}
public int getSwipeMaxDistance(){
return this.swipe_Max_Distance;
}
public int getSwipeMinDistance(){
return this.swipe_Min_Distance;
}
public int getSwipeMinVelocity(){
return this.swipe_Min_Velocity;
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
float velocityY) {
final float xDistance = Math.abs(e1.getX() - e2.getX());
final float yDistance = Math.abs(e1.getY() - e2.getY());
if(xDistance > this.swipe_Max_Distance || yDistance > this.swipe_Max_Distance)
return false;
velocityX = Math.abs(velocityX);
velocityY = Math.abs(velocityY);
boolean result = false;
if(velocityX > this.swipe_Min_Velocity && xDistance > this.swipe_Min_Distance){
if(e1.getX() > e2.getX()) // right to left
this.listener.onSwipe(SWIPE_LEFT);
else
this.listener.onSwipe(SWIPE_RIGHT);
result = true;
}
else if(velocityY > this.swipe_Min_Velocity && yDistance > this.swipe_Min_Distance){
if(e1.getY() > e2.getY()) // bottom to up
this.listener.onSwipe(SWIPE_UP);
else
this.listener.onSwipe(SWIPE_DOWN);
result = true;
}
return result;
}
@Override
public boolean onSingleTapUp(MotionEvent e) {
this.tapIndicator = true;
return false;
}
@Override
public boolean onDoubleTap(MotionEvent arg0) {
this.listener.onDoubleTap();;
return true;
}
@Override
public boolean onDoubleTapEvent(MotionEvent arg0) {
return true;
}
@Override
public boolean onSingleTapConfirmed(MotionEvent arg0) {
if(this.mode == MODE_DYNAMIC){ // we owe an ACTION_UP, so we fake an
arg0.setAction(ACTION_FAKE); //action which will be converted to an ACTION_UP later.
this.context.dispatchTouchEvent(arg0);
}
return false;
}
static interface SimpleGestureListener{
void onSwipe(int direction);
void onDoubleTap();
}
}
查看活动实施：
package com.example.EventsView;
import android.app.Activity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Toast;
import com.example.mobilefit.GuesterFilter.SimpleGestureListener;
public class BeginYourWorkout extends Activity implements SimpleGestureListener
{
private GuesterFilter detector;
protected void onCreate(Bundle savedInstanceState)
{
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
super.onCreate(savedInstanceState);
setContentView(R.layout.eventsView);
}
public boolean dispatchTouchEvent(MotionEvent me)
{
this.detector.onTouchEvent(me);
return super.dispatchTouchEvent(me);
}
@Override
public void onSwipe(int direction)
{
String str = "";
switch (direction) {
case GuesterFilter.SWIPE_RIGHT : str = "Swipe Right";
break;
case GuesterFilter.SWIPE_LEFT : str = "Swipe Left";
break;
case GuesterFilter.SWIPE_DOWN : str = "Swipe Down";
break;
case GuesterFilter.SWIPE_UP : str = "Swipe Up";
break;
}
Toast.makeText(this, str, Toast.LENGTH_SHORT).show();
}
@Override
public void onDoubleTap()
{
Toast.makeText(this, "Double Tap", Toast.LENGTH_SHORT).show();
}
public boolean onSingleTapUp(MotionEvent e)
{
Toast.makeText(this, "Double Tap", Toast.LENGTH_SHORT).show();
return false;
}
}
日志错误：
FATAL EXCEPTION: main
java.lang.NullPointerException
at com.example.myPackage.EventsView.dispatchTouchEvent(EventsView.java:27)
at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1901)
at android.view.View.dispatchPointerEvent(View.java:7419)
at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:3220)
at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:3165)
at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:4292)
at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:4271)
at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:4363)
at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:179)
at android.os.MessageQueue.nativePollOnce(Native Method)
at android.os.MessageQueue.next(MessageQueue.java:125)
at android.os.Looper.loop(Looper.java:124)
at android.app.ActivityThread.main(ActivityThread.java:5039)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)