android - 强制用户在对话框中选择选项

Question

第一次启动应用程序时，我想提示用户(通过对话框)选择他们的城市，然后这将保存他们的偏好并将适当的数据加载到 ListView 中。但是，我注意到对话框可以通过后退按钮关闭，或者按对话框外的任何地方，然后触发数据库的空值。

无论如何我可以强制对话框保持打开状态直到用户选择一个选项吗？

我已经实现了 .setCancelable(false) 但这似乎不起作用。我的代码如下，DialogSetup 是我正在使用的内部类。

如有任何帮助/想法，我们将不胜感激。

public class MainActivity extends ListActivity {
private Cursor lines;
private MetroSleepDb db;
private ListAdapter adapter;
public static final String PREFS_NAME = "METROSLEEP_PREFS";

@Override
protected void onCreate(Bundle savedInstanceState) {


    super.onCreate(savedInstanceState);



    chooseCityDialog();




}




public void setAdapters() {

    db = new MetroSleepDb(this);
    lines = db.getLines(); // you would not typically call this on the main thread
    //ListView listView = (ListView) findViewById(R.id.li);
    adapter = new SimpleCursorAdapter(this, android.R.layout.simple_list_item_1, 
            lines, 
            new String[] {"line_id"}, 
            new int[] {android.R.id.text1}, 0);


    getListView().setAdapter(adapter);
    getListView().setOnItemClickListener(onAnswerClicked);

}


public String getItem(int pos) {

    Cursor c = (Cursor) adapter.getItem(pos);
    String value = c.getString(c.getColumnIndex("line_id"));
    return value;
}

private OnItemClickListener onAnswerClicked = new OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position,
            long id) {

        String line_value = getItem(position);
        Intent intent = new Intent(MainActivity.this, ChooseStations.class);
        intent.putExtra("line", line_value);
        startActivity(intent);
    }

};

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


@Override
public boolean onOptionsItemSelected(MenuItem  item) {
    switch (item.getItemId()) {
    case android.R.id.home:
        // This ID represents the Home or Up button. In the case of this
        // activity, the Up button is shown. Use NavUtils to allow users
        // to navigate up one level in the application structure. For
        // more details, see the Navigation pattern on Android Design:
        //
        // http://developer.android.com/design/patterns/navigation.html#up-vs-back
        //
        NavUtils.navigateUpFromSameTask(this);
        return true;

    case R.id.menu_settings:
        Intent intent = new Intent(this, SettingsActivity.class);
        startActivity(intent);
        return true;
    }
    return super.onOptionsItemSelected(item);
}

public void chooseCityDialog() {
    DialogFragment newFragment = new DialogSetup();
    newFragment.show(getFragmentManager(), "citypref");
}

public static final class DialogSetup extends DialogFragment {
    public Dialog onCreateDialog(Bundle savedInstanceState) {

        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setTitle(R.string.prompt_choose_city)
               .setCancelable(false) 
               .setItems(R.array.Cities, new DialogInterface.OnClickListener() {
                   public void onClick(DialogInterface dialog, int which) {
                       //
               }
        });

        return builder.create();
    }



}

Answer 1

啊哈!你必须调用setCancelable(false)在 DialogFragment 上，而不是在 AlertDialog.builder 上。看到这个问题:AlertDialog's setCancelable(false) method not working .

DialogFragment.setCancelable(boolean cancelable) 的文档指出:

Control whether the shown Dialog is cancelable. Use this instead of directly calling Dialog.setCancelable(boolean), because DialogFragment needs to change its behavior based on this.

您只需添加 1 行代码:

public void chooseCityDialog() {
    DialogFragment newFragment = new DialogSetup();
    newFragment.setCancelable(false);
    newFragment.show(getFragmentManager(), "citypref");
}

此外，如果从 Dialog 返回的城市不知何故为 null，那么如果有一个默认城市可以回退，这将是一个很好的安全检查。