Question

我有一个警告对话框，其中包含一个选项列表和两个按钮：OK按钮和cancel按钮。下面的代码显示了我是如何实现它的。

private final Dialog createListFile(final String[] fileList) {
  AlertDialog.Builder builder = new AlertDialog.Builder(this);
  builder.setTitle("Compare with:");

  builder.setSingleChoiceItems(fileList, -1, new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {
      Log.d(TAG,"The wrong button was tapped: " + fileList[whichButton]);
    }
  });

  builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {}
  });

  builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {}
  });

  return builder.create();
}

我的目标是在点按OK按钮时获取所选单选按钮的名称。我试图将字符串保存在变量中，但在内部类中，可以只访问最终变量。有没有办法避免使用最终变量来存储选定的单选按钮？

Answer 1

使用最终变量显然不起作用（因为它只能在声明时分配一次）。所谓的“全局”变量通常是代码气味（特别是当它们成为Activity类的一部分时，通常是创建AlertDialogs的地方）。更干净的解决方案是将DialogInterface对象转换为AlertDialog，然后调用getListView（）。getCheckedItemPosition（）。像这样：

new AlertDialog.Builder(this)
        .setSingleChoiceItems(items, 0, null)
        .setPositiveButton(R.string.ok_button_label, new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int whichButton) {
                dialog.dismiss();
                int selectedPosition = ((AlertDialog)dialog).getListView().getCheckedItemPosition();
                // Do something useful withe the position of the selected radio button
            }
        })
        .show();

Answer 2

这已经得到了很好的解答，但我一直在寻找谷歌的这个答案，我想分享一个非匿名的类解决方案。我自己更喜欢可重复使用的课程，可能对其他人有帮助。

在此示例中，我使用DialogFragment实现并通过回调方法检索值。

从 Dialog 获取值的回调方法可以通过创建公共界面

来完成

public interface OnDialogSelectorListener {
    public void onSelectedOption(int selectedIndex);
}

同样DialogFragment实现DialogInterface.OnClickListener，这意味着您可以将正在实现的类注册为正在创建的DialogFragment的 OnClickListener 。 / p>

例如

public Dialog onCreateDialog(Bundle savedInstanceState) {
    final AlertDialog.Builder builder = new AlertDialog.Builder(this.getActivity());

    builder.setTitle(R.string.select);
    builder.setSingleChoiceItems(mResourceArray, mSelectedIndex, this);
    builder.setPositiveButton(R.string.ok, this);
    builder.setNegativeButton(R.string.cancel, this);
    return builder.create();
}

该行

builder.setSingleChoiceItems(mResourceArray, mSelectedIndex, this);

使用 mResourceArray 中存储的资源数组中的选项创建一个选择对话框。这也预先选择存储在 mSelectedIndex 中的选项索引，最后将this本身设置为 OnClickListener 。（如果这段话有点令人困惑，请参阅最后的完整代码）

现在，您可以使用 OnClick 方法获取对话框中的值

@Override
public void onClick(DialogInterface dialog, int which) {

    switch (which) {
        case Dialog.BUTTON_NEGATIVE: // Cancel button selected, do nothing
            dialog.cancel();
            break;

        case Dialog.BUTTON_POSITIVE: // OK button selected, send the data back
            dialog.dismiss();
            // message selected value to registered callbacks with the
                    // selected value.
            mDialogSelectorCallback.onSelectedOption(mSelectedIndex);
            break;

        default: // choice item selected
                    // store the new selected value in the static variable
            mSelectedIndex = which;
            break;
    }
}

这里发生的是当选择一个项目时，它存储在一个变量中。如果用户单击取消按钮，则不会发回任何更新，也不会发生任何更改。如果用户单击“确定”按钮，则会将值返回到通过创建的回调创建它的Activity。

例如，以下是如何从FragmentActivity创建对话框。

final SelectorDialog sd = SelectorDialog.newInstance(R.array.selector_array, preSelectedValue);
sd.show(getSupportFragmentManager(), TAG);

此处，资源数组_R.array.selector_array_是要在对话框中显示的字符串数组， preSelectedValue 是要在打开时选择的索引。

最后，您的FragmentActivity将实施OnDialogSelectorListener，并会收到回电消息。

public class MyActivity extends FragmentActivity implements OnDialogSelectorListener {
// ....

    public void onSelectedOption(int selectedIndex) {
        // do something with the newly selected index
    }
}

我希望这对某人有帮助，因为我花了很多时间去理解它。此类DialogFragment带有回调的完整实现就在这里。

public class SelectorDialog extends DialogFragment implements OnClickListener {
    static final String TAG = "SelectorDialog";

    static int mResourceArray;
    static int mSelectedIndex;
    static OnDialogSelectorListener mDialogSelectorCallback;

    public interface OnDialogSelectorListener {
        public void onSelectedOption(int dialogId);
    }

    public static DialogSelectorDialog newInstance(int res, int selected) {
        final DialogSelectorDialog dialog  = new DialogSelectorDialog();
        mResourceArray = res;
        mSelectedIndex = selected;

        return dialog;
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);

        try {
            mDialogSelectorCallback = (OnDialogSelectorListener)activity;
        } catch (final ClassCastException e) {
            throw new ClassCastException(activity.toString() + " must implement OnDialogSelectorListener");
        }
    }

    public Dialog onCreateDialog(Bundle savedInstanceState) {
        final AlertDialog.Builder builder = new AlertDialog.Builder(this.getActivity());

        builder.setTitle(R.string.select);
        builder.setSingleChoiceItems(mResourceArray, mSelectedIndex, this);
        builder.setPositiveButton(R.string.ok, this);
        builder.setNegativeButton(R.string.cancel, this);
        return builder.create();
    }

    @Override
    public void onClick(DialogInterface dialog, int which) {

        switch (which) {
            case Dialog.BUTTON_NEGATIVE:
                dialog.cancel();
                break;

            case Dialog.BUTTON_POSITIVE:
                dialog.dismiss();
                // message selected value to registered calbacks
                mDialogSelectorCallback.onSelectedOption(mSelectedIndex);
                break;

            default: // choice selected click
                mSelectedIndex = which;
                break;
        }

    }
}

评论中的问题如何从Fragment而不是Activity拨打此电话。

首先对DialogFragment进行一些更改。

删除onAttach事件，因为这不是此方案中最简单的方法。

添加新方法以添加对回调的引用

public void setDialogSelectorListener (OnDialogSelectorListener listener) {
    this.mListener = listener;
}

在Fragment

中实施听众

public class MyFragment extends Fragment implements SelectorDialog.OnDialogSelectorListener {
// ....

    public void onSelectedOption(int selectedIndex) {
        // do something with the newly selected index
    }
}

现在创建一个新实例并传入对Fragment的引用以使用它。

final SelectorDialog sd = SelectorDialog.newInstance(R.array.selector_array, preSelectedValue);
// this is a reference to MyFragment
sd.setDialogSelectorListener(this);
// mActivity is just a reference to the activity attached to MyFragment
sd.show(this.mActivity.getSupportFragmentManager(), TAG);

Answer 3

final CharSequence[] choice = {"Choose from Gallery","Capture a photo"};

int from; //This must be declared as global !

AlertDialog.Builder alert = new AlertDialog.Builder(activity);
alert.setTitle("Upload Photo");
alert.setSingleChoiceItems(choice, -1, new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        if (choice[which] == "Choose from Gallery") {
            from = 1;
        } else if (choice[which] == "Capture a photo") {
            from = 2;
        }
    }
});
alert.setPositiveButton("OK", new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        if (from == 0) {
            Toast.makeText(activity, "Select One Choice", 
                        Toast.LENGTH_SHORT).show();
        } else if (from == 1) {
            // Your Code
        } else if (from == 2) {
            // Your Code
        }
    }
});
alert.show();

Answer 4

尝试一下。

final String[] fonts = {"Small", "Medium", "Large", "Huge"};

AlertDialog.Builder builder = new AlertDialog.Builder(TopicDetails.this);
builder.setTitle("Select a text size");
builder.setItems(fonts, new DialogInterface.OnClickListener() {
  @Override
  public void onClick(DialogInterface dialog, int which) {
    if ("Small".equals(fonts[which])) {
      Toast.makeText(MainActivity.this,"you nailed it", Toast.LENGTH_SHORT).show();
    }
    else if ("Medium".equals(fonts[which])) {
      Toast.makeText(MainActivity.this,"you cracked it", Toast.LENGTH_SHORT).show();
    }
    else if ("Large".equals(fonts[which])){
      Toast.makeText(MainActivity.this,"you hacked it", Toast.LENGTH_SHORT).show();
    }
    else if ("Huge".equals(fonts[which])){
     Toast.makeText(MainActivity.this,"you digged it", Toast.LENGTH_SHORT).show();
    }
  // the user clicked on colors[which]
  }
});
builder.show();

Answer 5

正如其他人指出的那样，实现'com.google.android.material：material：1.0.0'更简单

有关更多信息，请参阅此材料指南。 https://material.io/develop/android/docs/getting-started/

CharSequence[] choices = {"Choice1", "Choice2", "Choice3"};
boolean[] choicesInitial = {false, true, false};
AlertDialog.Builder alertDialogBuilder = new MaterialAlertDialogBuilder(getContext())
    .setTitle(title)
    .setPositiveButton("Accept", null)
    .setNeutralButton("Cancel", null)
    .setMultiChoiceItems(choices, choicesInitial, new DialogInterface.OnMultiChoiceClickListener() {
      @Override
      public void onClick(DialogInterface dialog, int which, boolean isChecked) {

      }
    });
alertDialogBuilder.show();

Answer 6

Android AlertDialog 可用于通过“确定”和“取消”按钮显示对话框消息。它可以用来打扰并询问用户有关他/她选择继续还是终止的信息。AlertDialog单选项目示例由三个区域组成：标题，内容区域和操作按钮。 Android AlertDialog是Dialog类的子类。 MainActivity.kt

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val context = this
        button.setOnClickListener {
            val builder = MaterialAlertDialogBuilder(context)
            // dialog title
            builder.setTitle("Which is your favorite?")
            val colors = arrayOf(
                "African violet",
                "Alice blue",
                "Alloy orange",
                "Android green",
                "Amaranth pink",
                "Antique bronze"
            )
            // set single choice items
            builder.setSingleChoiceItems(
                colors, // array
                -1 // initial selection (-1 none)
            ){dialog, i ->}

            // alert dialog positive button
            builder.setPositiveButton("Submit"){dialog,which->
                val position = (dialog as AlertDialog).listView.checkedItemPosition
                // if selected, then get item text
                if (position !=-1){
                    val selectedItem = colors[position]
                    textView.text = "Favorite color : $selectedItem"
                }
            }
            // alert dialog other buttons
            builder.setNegativeButton("No",null)
            builder.setNeutralButton("Cancel",null)
            // set dialog non cancelable
            builder.setCancelable(false)
            // finally, create the alert dialog and show it
            val dialog = builder.create()
            dialog.show()
            // initially disable the positive button
            dialog.getButton(AlertDialog.BUTTON_POSITIVE).isEnabled = false
            // dialog list item click listener
            dialog.listView.onItemClickListener =
                OnItemClickListener { parent, view, position, id ->
                    // enable positive button when user select an item
                    dialog.getButton(AlertDialog.BUTTON_POSITIVE)
                        .isEnabled = position != -1
                }
        }
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/constraintLayout"
    tools:context=".MainActivity">
    <com.google.android.material.button.MaterialButton
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="24dp"
        android:text="Show Dialog"
        android:backgroundTint="#4B5320"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        tools:text="TextView"
        android:textAppearance="@style/TextAppearance.AppCompat.Large"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button" />
</androidx.constraintlayout.widget.ConstraintLayout>

如何使用单选复选框android在AlertDialog中选择一个条目？

6 个答案: