Question

我是Android新手，我正在尝试编写一个简单的虚拟应用程序来学习创建自己的View类等等。我为什么要这样做？我希望有一个由几个页面组成的UI，可以通过按下操作栏上的按钮来浏览。我现在想添加通过触摸手势导航的功能。然后我遇到了我试图用这个虚拟应用程序解决的问题，它与我原来的应用程序一样，只是更简单一点。

（以前）问题：片段的一侧有一个ScrollView，当你点击它们时它会吃掉触摸手势。

我读到了这一点并想通了我必须创建自己的FrameLayout和@Override onInterceptTouchEvent和onTouchEvent方法。我现在使用这个新的FrameLayout作为我的Fragment容器。然而，当我使用FragmentLayout中的ScrollView而不是LinearLayout（如此代码示例）测试应用程序时，它仍然无法正常工作。但在这一点上，这不是我最大的问题，我想我只需要对这两种方法进行一些工作就可以让它们按照我想要的方式工作。

此时我的应用程序在通过触摸手势交换片段时崩溃...按钮仍然有效。

我收到此错误（LogCat）：

06-18 14:34:03.295: W/dalvikvm(2983): threadid=1: thread exiting with uncaught exception (group=0x409f51f8)
06-18 14:34:03.305: E/AndroidRuntime(2983): FATAL EXCEPTION: main
06-18 14:34:03.305: E/AndroidRuntime(2983): java.lang.IllegalStateException: Activity has been destroyed
06-18 14:34:03.305: E/AndroidRuntime(2983):     at android.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1280)
06-18 14:34:03.305: E/AndroidRuntime(2983):     at android.app.BackStackRecord.commitInternal(BackStackRecord.java:541)
06-18 14:34:03.305: E/AndroidRuntime(2983):     at android.app.BackStackRecord.commit(BackStackRecord.java:525)
06-18 14:34:03.305: E/AndroidRuntime(2983):     at com.example.trysomething.MainActivity.switchFragment(MainActivity.java:97)
06-18 14:34:03.305: E/AndroidRuntime(2983):     at com.example.trysomething.MainActivity.navForward(MainActivity.java:74)

这是我的MainActivity：

public class MainActivity extends Activity {

    int pos;

    TouchInterceptingLayout mtil;

    CharSequence mTitle;
    String[] mTitles;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mtil = (TouchInterceptingLayout) findViewById(R.id.fragment_container);

        pos = 0;
        mTitle = getTitle();
        mTitles = getResources().getStringArray(R.array.dummy_seiten);

        if(savedInstanceState == null){
            switchFragment(0);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu){
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.main, menu);
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item){

        switch(item.getItemId()){
        case R.id.action_nav_back:
            navBackwards();
            break;
        case R.id.action_nav_forward:
            navForward();
            break;
        }

        return super.onOptionsItemSelected(item);
    }

    public void setTitle(CharSequence title){
        mTitle = title;
        getActionBar().setTitle(mTitle);
    }

    public void navForward(){
        if(pos == 2){
            pos = 0;
            switchFragment(pos);
        } else {
            pos += 1;
            switchFragment(pos);
        }
    }

    public void navBackwards(){
        if(pos == 0){
            pos = 2;
            switchFragment(pos);
        } else {
            pos -= 1;
            switchFragment(pos);
        }
    }

    public void switchFragment(int position){
        Fragment newFrag;
        Bundle args = new Bundle();
        args.putInt(DummyFragmentSimpleView.ARG_POSITION, position);
        newFrag = new DummyFragmentSimpleView();
        newFrag.setArguments(args);
        android.app.FragmentManager fm = getFragmentManager();
        FragmentTransaction ft = fm.beginTransaction();
        ft.replace(R.id.fragment_container, newFrag);
        ft.commit();
    }
}

这是我的DummyFragmentSimpleView（Java）：

public class DummyFragmentSimpleView extends Fragment {

public static String ARG_POSITION = "position";

Bundle args;

String[] dummyStringArray;
String[] nonsenseArray;

LayoutParams params;

public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);

    dummyStringArray = getResources().getStringArray(R.array.dummy_array);
    nonsenseArray = getResources().getStringArray(R.array.nonsense_array);
    params = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
    args = getArguments();
}

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){

    View mySimpleFrag = inflater.inflate(R.layout.fragment_notscrolling, container, false);

    ImageView image = (ImageView) mySimpleFrag.findViewById(R.id.image_container);
    String bild = getResources().getStringArray(R.array.dummy_seiten)[args.getInt(ARG_POSITION)];
    int bildId = getResources().getIdentifier(bild.toLowerCase(Locale.getDefault()), "drawable", getActivity().getPackageName());
    ((ImageView) image).setImageResource(bildId);

    LinearLayout dummyLayout = (LinearLayout) mySimpleFrag.findViewById(R.id.content_container);

    TextView t = (TextView) mySimpleFrag.findViewById(R.id.nonsense_text);
    t.setText(nonsenseArray[args.getInt(ARG_POSITION)]);

    for(int i = 0; i < dummyStringArray.length; i++){
        TextView text = new TextView(getActivity());
        text.setText(dummyStringArray[i]);
        text.setId(i);
        text.setLayoutParams(params);
        text.setTextSize(20);
        ((LinearLayout) dummyLayout).addView(text);         
    }

    getActivity().setTitle(bild);

    return mySimpleFrag;
}
}

这是简单视图的XML：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" 
    android:baselineAligned="false">

    <LinearLayout 
        android:id="@+id/left_panel"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:background="#C00000"
        android:gravity="center">

        <ImageView
            android:id="@+id/image_container"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>

    </LinearLayout>



        <LinearLayout
            android:id="@+id/right_panel"
            android:layout_weight="2"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <TextView 
                android:id="@+id/nonsense_text"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:textSize="30sp"
                android:textStyle="bold"/>

            <LinearLayout 
                android:id="@+id/content_container"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="vertical"/>

        </LinearLayout>



</LinearLayout>

这是我的TouchInterceptingLayout类：

public class TouchInterceptingLayout extends FrameLayout{

    boolean mIsNavigating = false;

    MotionEventHandler handler = new MotionEventHandler();

    public TouchInterceptingLayout(Context context) {
        super(context);
    }

    public TouchInterceptingLayout(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public TouchInterceptingLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        for(int i = 0; i < getChildCount(); i++){
            getChildAt(i).layout(left, top, right, bottom);
        }
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent event){

        float x1 = 0;
        float x2 = 0;

        final int action = event.getAction();

        if(action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP){
            mIsNavigating = false;
            return false;
        }

        switch (action){
        case MotionEvent.ACTION_DOWN:
            x1 = event.getX();
            break;
        case MotionEvent.ACTION_MOVE:
            return false;
        case MotionEvent.ACTION_UP:
            x2 = event.getX();
            if(Math.abs(x2 - x1) > 150){
                mIsNavigating = true;
                return true;
            } else {
                return false;
            }
        }
        return false;
    }

    @Override
    public boolean onTouchEvent(MotionEvent event){
        switch(event.getAction()){
        case MotionEvent.ACTION_DOWN:
            handler.setXOne(event.getX());
            return true;

        case MotionEvent.ACTION_UP:
            handler.setXTwo(event.getX());
            handler.setDelta();
            handler.performAction();
            break;
        }
        return super.onTouchEvent(event);
    }
}

MotionEventHandler类：

public class MotionEventHandler {

    static final int MIN_X_DISTANCE = 150;
    public float x1 = 0;
    public float x2 = 0;
    public float deltaX = 0;
    MainActivity myBoss = new MainActivity();

    public MotionEventHandler(){
    }

    public void setXOne(float x){
        x1 = x;
    }

    public void setXTwo(float x){
        x2 = x;
    }

    public float getXOne(){
        return x1;
    }

    public float getXTwo(){
        return x2;
    }

    public void setDelta(){
        deltaX = x2 - x1;
    }

    public float getDelta(){
        return deltaX;
    }

    public boolean isPageBeingSwapped(){
        if (Math.abs(deltaX)<MIN_X_DISTANCE){
            return false;
        } else {
            return true;
        }
    }

    public void performAction(){
        if(isPageBeingSwapped()){
            if(deltaX < 0){
                myBoss.navBackwards();
            } else {
                myBoss.navForward();
            }
        }
    }
}

activity_main.xml中：

<?xml version="1.0" encoding="utf-8"?>
    <com.example.trysomething.TouchInterceptingLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

我希望有人能提供帮助，我的问题描述不会太混乱，我的问题也不会太愚蠢......; s

提前致谢！

Answer 1

您的问题就在MotionEventHandler

中

public class MotionEventHandler {

    static final int MIN_X_DISTANCE = 150;
    public float x1 = 0;
    public float x2 = 0;
    public float deltaX = 0;

    // -- Right here --
    MainActivity myBoss = new MainActivity();

    // The rest of your code
}

你得到的错误有点误导，因为并不是你的MainActivity被破坏了。此问题是您正在使用的不是屏幕上可见的那个。几乎在所有情况下，您都不希望通过调用其构造函数来实例化Activity。

幸运的是，对此的修复相对容易。您的MotionEventHandler应该有一个构造函数，其中包含MainActivity，如下所示：

public MotionEventHandler(MainActivity mainAct) {
    myBoss = mainAct;
}

在你的TouchInterceptingLayout中，你应该在构造函数中实例化处理程序。

public class TouchInterceptingLayout extends FrameLayout{
    MotionEventHandler handler;

    public TouchInterceptingLayout(Context context) {
        super(context);
        if(context instanceof MainActivity) {
            handler =  = new MotionEventHandler((MainActivity) context)
        }
        else {
            // Not a valid context
        }
    }
    public TouchInterceptingLayout(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public TouchInterceptingLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        if(context instanceof MainActivity) {
            handler =  = new MotionEventHandler((MainActivity) context)
        }
        else {
            // Not a valid context
        }
    }

    // The rest of your code
}

更换Fragment时正在销毁活动

1 个答案: