android 返回上一个视图

Question

我正在开发一个 android 应用程序，当涉及到没有视图可返回的状态时，我想在返回时退出应用程序。在此之前，它应该会返回到上一个按后退的视图。我该怎么做。

我需要什么

返回上一视图。
如果您再也回不去了，敬酒并要求退出应用程序。

我的代码

@Override
    public void onBackPressed() {



            DialogInterface.OnClickListener dialogInterface = new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {
                    switch (which) {
                    case DialogInterface.BUTTON_POSITIVE:


                        Intent intent = new Intent(Intent.ACTION_MAIN);
                        intent.addCategory(Intent.CATEGORY_HOME);
                        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                        startActivity(intent);
                        finish();

                        break;

                    case DialogInterface.BUTTON_NEGATIVE:


                    }

                    commonVariable.setSteps(0);

                }
            };

            AlertDialog.Builder builder = new AlertDialog.Builder(
                    MainActivity.this);
            builder.setMessage("Are you sure to exit the app?")
                    .setPositiveButton("Yes", dialogInterface)
                    .setNegativeButton("No", dialogInterface).show();



        }
    }

Answer 1

您可以为此使用 Fragment Manager。

在 Fragman Manager 中，您有一个名为的方法：

getBackStackEntryCount()

如果这个 returns 0 你可以关闭你的应用程序，否则你就回去。

Answer 2

在你的activity中：

@Override
public void onBackPressed() {
    Fragment fragment = getCurrentFragment();
    boolean isHandled = false;
    if(fragment != null && (fragment instanceof BaseFragment)){
        isHandled = ((BaseFragment) fragment).onBackPressed();
    }
    if(!isHandled){
        super.onBackPressed();
    }
}

private Fragment getCurrentFragment() {
    Fragment fragment = null;
    FragmentManager fragmentManager = getFragmentManager();
    if(fragmentManager != null){
        fragment = fragmentManager.findFragmentById(R.id.content_frame);
    }
    return fragment;
}

在 BaseFragment 中：

public boolean onBackPressed()
    FragmentManager manager = getFragmentManager();
    if(manager != null){
        int count = manager.getBackStackEntryCount();
        if(count > 0) {
            manager.popBackStack();
        } else {
            if(isAdded()){
                Toast.makeText(getActivity(), "Are you sure?", Toast.LENGTH_SHORT).show();
                showDialog();
            }
        }
    }
    return true;
}
...
onPositiveButtonClick(){
   getActivity().finish();
}

Answer 3

试试这个，

@Override
public void onBackPressed(){

    if(fragment.getBackStackEntryCount() != 0){
        DialogInterface.OnClickListener dialogInterface = new DialogInterface.OnClick....
        ....
    }
    else{
        new AlertDialog.Builder(this)
       .setMessage("Are you sure you want to exit?")
       .setCancelable(false)
       .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
                YourActivity.this.finish();
           }
       })
       .setNegativeButton("No", null)
       .show();
    }
}

Answer 4

解决方案

@Override 
    public void onBackPressed() { 
        if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
            getSupportFragmentManager().popBackStack(); 
        } else { 
            DialogInterface.OnClickListener dialogInterface = new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {
                    switch (which) {
                    case DialogInterface.BUTTON_POSITIVE:


                        Intent intent = new Intent(Intent.ACTION_MAIN);
                        intent.addCategory(Intent.CATEGORY_HOME);
                        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                        startActivity(intent);
                        finish();

                        break;

                    case DialogInterface.BUTTON_NEGATIVE:


                    }

                    commonVariable.setSteps(0);

                }
            };

            AlertDialog.Builder builder = new AlertDialog.Builder(
                    MainActivity.this);
            builder.setMessage("Are you sure to exit the app?")
                    .setPositiveButton("Yes", dialogInterface)
                    .setNegativeButton("No", dialogInterface).show();
        }
    }

android 返回上一个视图

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