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📜  Android-警报对话框

📅  最后修改于: 2021-01-05 05:04:54             🧑  作者: Mango

对话框是一个小窗口，提示用户做出决定或输入其他信息。

在您的应用程序中，有时候，如果您想让用户根据用户采取的任何特定操作，在是或否之间做出决定，方法是保持相同的活动并且不更改屏幕，则可以使用“警告对话框”。

为了创建警报对话框，您需要创建一个AlertDialogBuilder对象，该对象是AlertDialog的内部类。其语法如下

AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(this);

现在，您必须使用AlertDialogBuilder类的对象设置正(是)或负(否)按钮。它的语法是

alertDialogBuilder.setPositiveButton(CharSequence text, 
   DialogInterface.OnClickListener listener)
alertDialogBuilder.setNegativeButton(CharSequence text, 
   DialogInterface.OnClickListener listener)

除此之外，您还可以使用builder类提供的其他功能来自定义警报对话框。这些在下面列出

Sr.No Method type & description
1

setIcon(Drawable icon)

This method set the icon of the alert dialog box.
2

setCancelable(boolean cancel able)

This method sets the property that the dialog can be cancelled or not
3

setMessage(CharSequence message)

This method sets the message to be displayed in the alert dialog
4

setMultiChoiceItems(CharSequence[] items, boolean[] checkedItems, DialogInterface.OnMultiChoiceClickListener listener)

This method sets list of items to be displayed in the dialog as the content. The selected option will be notified by the listener
5

setOnCancelListener(DialogInterface.OnCancelListener onCancelListener)

This method Sets the callback that will be called if the dialog is cancelled.
6

setTitle(CharSequence title)

This method set the title to be appear in the dialog

创建并设置对话框构建器之后，您将通过调用构建器类的create()方法来创建警报对话框。它的语法是

AlertDialog alertDialog = alertDialogBuilder.create();
alertDialog.show();

这将创建警报对话框，并将其显示在屏幕上。

对话片段

在进入示例之前，我们需要了解对话框片段。对话框片段是可以在对话框中显示片段的片段

public class DialogFragment extends DialogFragment {
   @Override
   public Dialog onCreateDialog(Bundle savedInstanceState) {
      // Use the Builder class for convenient dialog construction
      AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
      builder.setPositiveButton(R.string.fire, new DialogInterface.OnClickListener() {
         public void onClick(DialogInterface dialog, int id) {
            toast.makeText(this,"enter a text here",Toast.LENTH_SHORT).show();
         }
      })
      .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
         public void onClick(DialogInterface dialog, int id) {
            finish();
         });
         // Create the AlertDialog object and return it
         return builder.create();
      }
   }
}

列表对话框

它用于在对话框中显示项目列表。假设用户需要选择一个项目列表，或者需要从多个项目列表中单击一个项目，在这种情况下，我们可以使用列表对话框。

public Dialog onCreateDialog(Bundle savedInstanceState) {
   AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
   builder.setTitle(Pick a Color)
   
   .setItems(R.array.colors_array, new DialogInterface.OnClickListener() {
      public void onClick(DialogInterface dialog, int which) {
         // The 'which' argument contains the index position
         // of the selected item
      }
   });
   return builder.create();
}

单选列表对话框

它曾经用来在对话框中添加单选列表。我们可以根据用户的选择进行选择或取消选择。

public Dialog onCreateDialog(Bundle savedInstanceState) {
   mSelectedItems = new ArrayList();
   AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
   
   builder.setTitle("This is list choice dialog box");
   .setMultiChoiceItems(R.array.toppings, null,
      new DialogInterface.OnMultiChoiceClickListener() {
      @Override
      public void onClick(DialogInterface dialog, int which, boolean isChecked) {
         
         if (isChecked) {
            // If the user checked the item, add it to the selected items
            mSelectedItems.add(which);
         }
         
         else if (mSelectedItems.contains(which)) {
            // Else, if the item is already in the array, remove it 
            mSelectedItems.remove(Integer.valueOf(which));
         }
      }
   })
   
   // Set the action buttons
   .setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
      @Override
      public void onClick(DialogInterface dialog, int id) {
         // User clicked OK, so save the mSelectedItems results somewhere
         // or return them to the component that opened the dialog
         ...
      }
   })
   
   .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
      @Override
      public void onClick(DialogInterface dialog, int id) {
         ...
      }
   });
   return builder.create();
}

例

以下示例演示了在Android中使用AlertDialog的方法。

要试验该示例，您需要在仿真器或实际设备上运行它。

Steps Description
1 You will use Android studio to create an Android application and name it as My Application under a package com.example.sairamkrishna.myapplication.
2 Modify src/MainActivity.java file to add alert dialog code to launch the dialog.
3 Modify layout XML file res/layout/activity_main.xml add any GUI component if required.
4 No need to change default string constants. Android studio takes care of default strings at values/string.xml
5 Run the application and choose a running android device and install the application on it and verify the results.

这是src / MainActivity.java的修改后的代码

package com.example.sairamkrishna.myapplication;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity {
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
   }

   public void open(View view){
      AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(this);
      alertDialogBuilder.setMessage("Are you sure,
         You wanted to make decision");
      alertDialogBuilder.setPositiveButton("yes", 
         new DialogInterface.OnClickListener() {
         @Override
         public void onClick(DialogInterface arg0, int arg1) {
            Toast.makeText(MainActivity.this,"You clicked yes 
               button",Toast.LENGTH_LONG).show();
         }
      });

      alertDialogBuilder.setNegativeButton("No",new DialogInterface.OnClickListener() {
         Override
         public void onClick(DialogInterface dialog, int which) {
            finish();
         }
      });

      AlertDialog alertDialog = alertDialogBuilder.create();
      alertDialog.show();
   }
}

这是res / layout / activity_main.xml的修改后的代码

在下面的代码中abc表示tutorialspoint.com的徽标

这是Strings.xml


    My Application

这是AndroidManifest.xml的默认代码

让我们尝试运行您的应用程序。我假设您已将实际的Android Mobile设备与计算机连接。要从Android Studio运行该应用，请打开您项目的活动文件之一，然后点击运行Eclipse运行图标工具栏中的图标。在启动应用程序之前，] Android studio将显示以下窗口，以选择要在其中运行Android应用程序的选项。

环形相机教程

选择一个选项，然后单击它。假设，如果您单击“是”按钮，则结果如下

环形相机教程

如果您单击无按钮，它将调用finish()并关闭您的应用程序。