onTouchListener 检测错误的动态创建的卡片视图

Question

我刚刚学会了如何动态创建卡片视图。我正在使用按钮来创建一个卡片视图，并且我已经将 onTouchListener 设置为它。当我只创建一张卡片时，onTouchListener 工作正常，但是一旦我再创建一张卡片，onTouchListener 就无法按预期工作。当我有 2 张卡并尝试移动第一张卡时，它会移动第二张而不是第一张。

public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {

Context context;
ImageView imageView;
RelativeLayout relativeLayout;
static int pos=0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    context=this;
    relativeLayout=(RelativeLayout)findViewById(R.id.rl_layout);

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.setDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
}



@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {

        CreateCardViewWithoutImageView();

        return true;
    }

    return super.onOptionsItemSelected(item);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    return true;
}

public void CreateCardViewWithoutImageView(){

    final CardView cardview=new CardView(context);

    cardview.setId(++pos);
    cardview.setLayoutParams((new CardView.LayoutParams(600, 600)));
    cardview.setContentPadding(25,25,25,25);
    cardview.setCardBackgroundColor(Color.MAGENTA);

    relativeLayout.addView(cardview);

}

private final View.OnTouchListener mListener = new View.OnTouchListener() {
    @Override
    public boolean onTouch(View card, MotionEvent event) {
        // The View (v) here is a CardView as the onTouchListener is set to it
        RelativeLayout.LayoutParams layoutParamsRL = (RelativeLayout.LayoutParams) ((CardView) card).getLayoutParams();
        float dx = 0, dy = 0, x = 0, y = 0;

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN: {
                card.bringToFront();
                dx = event.getRawX() - layoutParamsRL.leftMargin;
                dy = event.getRawY() - layoutParamsRL.topMargin;
            }
            break;
            case MotionEvent.ACTION_MOVE: {
                x = event.getRawX();
                y = event.getRawY();
                layoutParamsRL.leftMargin = (int) (x - dx);
                layoutParamsRL.topMargin = (int) (y - dy);
                card.setLayoutParams(layoutParamsRL);
            }
            break;
            case MotionEvent.ACTION_UP: {

            }
            break;
        }
        return true;
    }
};

}

Answer 1

这是因为您的 cardview 变量是全局变量。所以每次你创建一个新的 CardView 时，它都会被替换，所以监听器总是使用最后一个创建的 CardView。 你应该这样做：

// Note: By the way, you should NOT use a capital letter to name a function
public void createCardViewWithoutImageView(){

    //CardView
    final CardView cardview = new CardView(context);

    //....

}

layoutParamsRL 也会遇到同样的问题，因为它也应该是本地的。

编辑

    // Context context; // You don't need to store the context here as you are in the activity
//    CardView cardview; // Don't need to be global
//    RelativeLayout.LayoutParams layoutParamsRL; // Don't need to be global
    ImageView imageView;
    RelativeLayout relativeLayout;
    static int pos = 0; // Are you sure it needs to be a static field?

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

//        context=this;
        relativeLayout = (RelativeLayout) findViewById(R.id.rl_layout);

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
    }


    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {

            createCardViewWithoutImageView();

            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        return true;
    }

    public void createCardViewWithoutImageView() {

        //CardView
        CardView cardview = new CardView(MainActivity.this);

        cardview.setId(++pos);
        cardview.setLayoutParams((new CardView.LayoutParams(600, 600)));
        cardview.setContentPadding(25, 25, 25, 25);
        cardview.setCardBackgroundColor(Color.MAGENTA);
        cardview.setOnTouchListener(mListener);

        relativeLayout.addView(cardview);
    }

    private final View.OnTouchListener mListener = new View.OnTouchListener() {

        float dx, dy; // Moved outside the onTouch method in order to them to keep their value.

        @Override
        public boolean onTouch(View card, MotionEvent event) {
            Log.d("OnTouchListener", "don't touch me :p");

            // The View (v) here is a CardView as the onTouchListener is set to it
            RelativeLayout.LayoutParams layoutParamsRL = (RelativeLayout.LayoutParams) ((CardView) card).getLayoutParams();
            float x = 0, y = 0;

            switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN: {
                    card.bringToFront();
                    dx = event.getRawX() - layoutParamsRL.leftMargin;
                    dy = event.getRawY() - layoutParamsRL.topMargin;
                }
                break;
                case MotionEvent.ACTION_MOVE: {
                    x = event.getRawX();
                    y = event.getRawY();
                    layoutParamsRL.leftMargin = (int) (x - dx);
                    layoutParamsRL.topMargin = (int) (y - dy);
                    card.setLayoutParams(layoutParamsRL);
                }
                break;
                case MotionEvent.ACTION_UP: {

                }
                break;
            }
            return true;
        }
    };

Answer 2

1- 变量是全局的，所以你需要在上面提到的内部方法中定义 2-您可以使用另一种方法轻松更改其属性，并将 cardview 对象作为参数传递给它 3-您可以保留全局对象来表示选定的卡片视图，因为在 touchevent 方法中会将触发事件的卡片视图分配给全局并用它做你想做的事情

Answer 3

//创建全局对象以在分配新属性时根据需要使用它

CardView selectedCardview;
@Override
protected void onCreate(Bundle savedInstanceState) { //....... }

//将创建内部对象

public void CreateCardViewWithoutImageView(){
    CardView cardview = new CardView(context);
    //Setting the default property u want:)
    cardview.setId(++pos);
    cardview.setLayoutParams((new CardView.LayoutParams(600, 600)));
    .......
    final CardView tempCardView=cardview;
    cardview.setOnTouchListener(new View.OnTouchListener() {
    @Override
    public boolean onTouch(View v, MotionEvent event) {
        switch(event.getAction())
        {
            case MotionEvent.ACTION_DOWN :
            {
              selectedCardview=tempCardView;
              .........and adding action as u want
            }
             ........... add another cases 
        }

    }
    ...........
}

现在你使用的 selectedCardview 将代表你触摸它的 cardview，并且很容易将其属性设置为全局

void setProperty(){
    /******** add what u want here********/
    selectedCardview.setBackgroundColor(Color.RED);
}