使用final变量显然是行不通的（因为它只能在声明时赋值一次）。所谓的“全局”变量通常是一种代码气味（特别是当它们成为Activity类的一部分时，Activity类通常是创建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（）。如下所示：

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();

这个问题已经得到了很好的回答，但是我一直在谷歌上找到这个答案，我想分享一个非匿名类的解决方案。我自己更喜欢可重用的类，可能对其他人有帮助。
在本例中，我使用DialogFragment实现，并通过 callback 方法检索值。
从 Dialog 获取值的 callback 方法可以通过创建公共接口来完成

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

此外，DialogFragment实现了DialogInterface.OnClickListener，这意味着您可以将已实现的类注册为正在创建的DialogFragment的 OnClickListener。
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();
}

这条线
builder.setSingleChoiceItems(mResourceArray, mSelectedIndex, this);
使用存储在 mResourceArray 中的 *resource数组 * 中的选项创建一个选择对话框。这还会从存储在 mSelectedIndex 中的选项中预先选择一个选项索引，最后将this本身设置为 OnClickListener。（如果本段有点混乱，请参阅末尾的完整代码）
现在，您可以使用 OnClick 方法获取来自对话框的值

@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;
    }
}

这里发生的事情是，当一个项目被选中时，它被存储在一个变量中。如果用户点击 Cancel 按钮，没有更新被发回，也没有任何变化。如果用户点击OK按钮，它通过创建的 callback 将值返回给创建它的Activity。
作为示例，下面是如何从FragmentActivity创建对话框。

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

这里，资源数组_R.array.selector_array_是要在对话框中显示的字符串数组，preSelectedValue 是打开时要选择的索引。
最后，FragmentActivity将实现OnDialogSelectorListener并接收回调消息。

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

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

我希望这对某些人有帮助，因为我花了很多努力去理解它。这里有一个带有 callback 的DialogFragment类型的完整实现。

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;
        }

    }
}

来自评论的问题如何从Fragment而不是Activity调用此函数。

首先对DialogFragment进行一些更改。
删除onAttach事件，因为这不是本场景中最简单的方法。
添加新方法以添加对回调的引用

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

在Fragment中实现监听器

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

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

现在创建一个新示例，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);

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();

正如其他人所指出的，**实现“com.google.android.material：material：1. 0. 0”**它更简单
请参阅本材料指南了解更多信息。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();

试试这个。

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();