1

我是 Android 新手,正在尝试编写一个简单的虚拟应用程序来学习有关创建自己的视图类等的知识。我为什么要这样做?我想要一个由多个页面组成的 UI,可以通过按下操作栏上的按钮进行导航。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,它与我的原始应用程序相同,只是更简单一些。

以前的)问题:片段的一侧确实有一个 ScrollView,当您单击它们时,它会吃掉触摸手势。

我读到了这篇文章,发现我必须创建自己的 FrameLayout 和 @Override onInterceptTouchEvent 和 onTouchEvent 方法。我现在使用这个新的 FrameLayout 作为我的片段容器。然而,当我在 FragmentLayout 中使用 ScrollView 而不是 LinearLayout(如本代码示例中)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,我想我只需要在这两种方法上做一些工作就可以让它们按照我的意愿工作。

此时,当通过触摸手势交换片段时,我的应用程序崩溃......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)

这是我的主要活动:

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();
            }
        }
    }
}

活动主.xml:

<?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"/>

我希望有人可以提供帮助,并且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!

4

1 回答 1

0

您的问题就出现在您的MotionEventHandler

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
}

您得到的错误有点误导,因为这并不是您的MainActivity已被破坏。这个问题是您正在使用的那个不是屏幕上可见的那个。几乎在所有情况下,您都不想Activity通过调用其构造函数来实例化 an。


幸运的是,解决这个问题相对容易。您MotionEventHandler应该有一个构造函数,它接受MainActivity以下内容:

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

在您TouchInterceptingLayout的构造函数中,您应该实例化处理程序。

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
}
于 2014-06-18T13:35:37.973 回答