Die Anleitung zu Android AlertDialog

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1- Android AlertDialog

Android AlertDialog ist ein Dialogfeld, in dem eine Nachricht angezeigt wird und das 1, 2 oder 3 Buttons unterstützt. Es macht es einfach, einen Dialog mit nur wenigen Codezeilen zu erstellen.
AlertDialog besteht aus 3 Regionen:
  1. Titelbereich (Title area)
  2. Inhaltsbereich (Content area)
  3. Tastenbereich (Buttons area)
Landscape screen
Portrait screen

Title area

Verwenden Sie die Methoden setTitle(), setIcon() um Titel und Symbol für das Dialogfeld festzulegen, das im Title area angezeigt wird. Verwenden Sie andernfalls die Methode setCustomTitle(View), wenn Sie einen benutzerdefinierten Title area haben möchten.

Content area

Im Content area können eine Nachricht, eine Liste mit Optionen usw. angezeigt werden.

Buttons area

Dieser Bereich verfügt über maximal 3 Buttons: Positive button, Negative button, Neutral button, wobei die ersten 2 Buttons Text & Icon unterstützen, während die Neutral button nur Text unterstützt. Sie können das Icon jedoch mit einem kleinen Trick anzeigen lassen (Weitere Informationen finden Sie im Beispiel). 

2- Zum Beispiel: AlertDialog (1)

Das Beispiel -Vorschau
AlertButtonExample0.java
package org.o7planning.alertdialogexample;

import android.content.Context;
import android.content.DialogInterface;
import android.graphics.drawable.Drawable;
import android.widget.Toast;

import androidx.appcompat.app.AlertDialog;

public class AlertDialogExample0 {

    public static void showAlertDialog(final Context context)  {
        final Drawable positiveIcon = context.getResources().getDrawable(R.drawable.icon_positive);
        final Drawable negativeIcon = context.getResources().getDrawable(R.drawable.icon_negative);
        final Drawable neutralIcon = context.getResources().getDrawable(R.drawable.icon_neutral);

        AlertDialog.Builder builder = new AlertDialog.Builder(context);

        // Set Title and Message:
        builder.setTitle("Title").setMessage("This is a message");

        //
        builder.setCancelable(true);
        builder.setIcon(R.drawable.icon_title);

        // Create "Positive" button with OnClickListener.
        builder.setPositiveButton("Positive", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                Toast.makeText(context,"You choose positive button",
                        Toast.LENGTH_SHORT).show();
            }
        });
        builder.setPositiveButtonIcon(positiveIcon);

        // Create "Negative" button with OnClickListener.
        builder.setNegativeButton("Negative", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                Toast.makeText(context,"You choose positive button",
                        Toast.LENGTH_SHORT).show();
                //  Cancel
                dialog.cancel();
            }
        });
        builder.setNegativeButtonIcon(negativeIcon);

        // Create "Neutral" button with OnClickListener.
        builder.setNeutralButton("Neutral", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                //  Action for 'NO' Button
                Toast.makeText(context,"You choose neutral button",
                        Toast.LENGTH_SHORT).show();
            }
        });
        builder.setNeutralButtonIcon(neutralIcon); // Not working!!!

        // Create AlertDialog:
        AlertDialog alert = builder.create();
        alert.show();
    }
}

3- Zum Beispiel AlertDialog (2)

AlertDialogExample2.java
package org.o7planning.alertdialogexample;

import android.app.Activity;
import android.content.Context;
import android.content.DialogInterface;
import android.graphics.drawable.Drawable;
import android.widget.Toast;

import androidx.appcompat.app.AlertDialog;

public class AlertDialogExample2 {

    public static void showAlertDialog(final Context context)  {
        final Drawable positiveIcon = context.getResources().getDrawable(R.drawable.icon_positive);
        final Drawable negativeIcon = context.getResources().getDrawable(R.drawable.icon_negative);

        AlertDialog.Builder builder = new AlertDialog.Builder(context);

        // Set Title and Message:
        builder.setTitle("Confirmation").setMessage("Do you want to close this app?");

        //
        builder.setCancelable(true);
        builder.setIcon(R.drawable.icon_title);

        // Create "Yes" button with OnClickListener.
        builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                Toast.makeText(context,"You choose Yes button",
                        Toast.LENGTH_SHORT).show();
                Activity activity = (Activity) context;
                activity.finish();
            }
        });
        builder.setPositiveButtonIcon(positiveIcon);

        // Create "No" button with OnClickListener.
        builder.setNegativeButton("No", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                Toast.makeText(context,"You choose No button",
                        Toast.LENGTH_SHORT).show();
                //  Cancel
                dialog.cancel();
            }
        });
        builder.setNegativeButtonIcon(negativeIcon);

        // Create AlertDialog:
        AlertDialog alert = builder.create();
        alert.show();
    }
}

4- Zum Beispiel AlertDialog (List)

Dies ist ein Beispiel für den AlertDialog mit einer Liste verschiedener Optionen, die der Benutzer auswählen kann:
AlertDialogListExample.java
package org.o7planning.alertdialogexample;

import android.app.Activity;
import android.content.Context;
import android.content.DialogInterface;
import android.graphics.drawable.Drawable;
import android.widget.Toast;

import androidx.appcompat.app.AlertDialog;

public class AlertDialogListExample {

    public static void showAlertDialog(final Activity activity)  {
        final Drawable negativeIcon = activity.getResources().getDrawable(R.drawable.icon_negative);

        AlertDialog.Builder builder = new AlertDialog.Builder(activity);

        // Set Title.
        builder.setTitle("Select an Animal");

        // Add a list
        final String[] animals = {"Horse", "Cow", "Camel", "Sheep", "Goat"};
        builder.setItems(animals, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                String animal = animals[which];

                dialog.dismiss(); // Close Dialog
                // Do some thing....
                // For example: Call method of MainActivity.
                Toast.makeText(activity,"You select: " + animal,
                        Toast.LENGTH_SHORT).show();
                // activity.someMethod(animal);
            }
        });

        //
        builder.setCancelable(true);
        builder.setIcon(R.drawable.icon_title);

        // Create "Cancel" button with OnClickListener.
        builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                Toast.makeText(activity,"You choose No button",
                        Toast.LENGTH_SHORT).show();
                //  Cancel
                dialog.cancel();
            }
        });
        builder.setNegativeButtonIcon(negativeIcon);

        // Create AlertDialog:
        AlertDialog alert = builder.create();
        alert.show();
    }

}

5- Zum Beispiel AlertDialog (Single Choice)

AlertDialogSingleChoiceExample.java
package org.o7planning.alertdialogexample;

import android.app.Activity;
import android.content.DialogInterface;
import android.widget.Toast;

import androidx.appcompat.app.AlertDialog;

import java.util.HashSet;
import java.util.Set;

public class AlertDialogSingleChoiceExample {


    public static void showAlertDialog(final Activity activity)  {
        AlertDialog.Builder builder = new AlertDialog.Builder(activity);

        // Set Title.
        builder.setTitle("Select an Animal");

        // Add a list
        final String[] animals = {"Horse", "Cow", "Camel", "Sheep", "Goat"};

        int checkedItem = 3; // Sheep
        final Set<String> selectedItems = new HashSet<String>();
        selectedItems.add(animals[checkedItem]);

        builder.setSingleChoiceItems(animals, checkedItem, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                // Do Something...
                selectedItems.clear();
                selectedItems.add(animals[which]);
            }
        });

        //
        builder.setCancelable(true);
        builder.setIcon(R.drawable.icon_title);

        // Create "Yes" button with OnClickListener.
        builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                if(selectedItems.isEmpty()) {
                    return;
                }
                String animal = selectedItems.iterator().next();

                // Close Dialog
                dialog.dismiss();
                // Do something, for example: Call a method of Activity...
                Toast.makeText(activity,"You select " + animal,
                        Toast.LENGTH_SHORT).show();

            }
        });

        // Create "Cancel" button with OnClickListener.
        builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                Toast.makeText(activity,"You choose Cancel button",
                        Toast.LENGTH_SHORT).show();
                //  Cancel
                dialog.cancel();
            }
        });

        // Create AlertDialog:
        AlertDialog alert = builder.create();
        alert.show();
    }

}

6- Zum Beispiel: AlertDialog (Multi Choice)

AlertDialogMultiChoiceExample.java
package org.o7planning.alertdialogexample;

import android.app.Activity;
import android.content.DialogInterface;
import android.widget.Toast;

import androidx.appcompat.app.AlertDialog;

import java.util.HashSet;
import java.util.Set;

public class AlertDialogMultiChoiceExample {


    public static void showAlertDialog(final Activity activity)  {
        AlertDialog.Builder builder = new AlertDialog.Builder(activity);

        // Set Title.
        builder.setTitle("Select an Animal");

        // Add a list
        final String[] animals = {"Horse", "Cow", "Camel", "Sheep", "Goat"};

        final boolean[] checkedInfos = new boolean[]{false, false, false, true, false}; // Sheep


        builder.setMultiChoiceItems(animals, checkedInfos, new DialogInterface.OnMultiChoiceClickListener()  {
            @Override
            public void onClick(DialogInterface dialog, int which, boolean isChecked) {
                checkedInfos[which] = isChecked;
            }
        });

        //
        builder.setCancelable(true);
        builder.setIcon(R.drawable.icon_title);

        // Create "Yes" button with OnClickListener.
        builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                // Close Dialog
                dialog.dismiss();

                String s= null;
                for(int i=0; i< animals.length;i++)  {
                    if(checkedInfos[i]) {
                        if(s == null)  {
                            s = animals[i];
                        } else {
                            s+= ", " + animals[i];
                        }
                    }
                }
                s = s == null? "":s;

                // Do something, for example: Call a method of Activity...
                Toast.makeText(activity,"You select " + s,
                        Toast.LENGTH_SHORT).show();
            }
        });

        // Create "Cancel" button with OnClickListener.
        builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                Toast.makeText(activity,"You choose Cancel button",
                        Toast.LENGTH_SHORT).show();
                //  Cancel
                dialog.cancel();
            }
        });

        // Create AlertDialog:
        AlertDialog alert = builder.create();
        alert.show();
    }

}

7- Zum Beispiel: anpassende Title Area

Durch die Anwendung der Methode setCustomTitle(View) können Sie den Title area (Titelbereich) von AlertDialog anpassen:
Verwenden Sie wahrscheinlich die Android Resource File, um die Interface von Title area zu erstellen.
AlertDialog.Builder builder = new AlertDialog.Builder(context);

// Custom Title Area.
LayoutInflater inflater = context.getLayoutInflater();
View view = inflater.inflate(R.layout.layout_custom_title, null);
builder.setCustomTitle(view);
...
        
// Create AlertDialog:
AlertDialog alert = builder.create();
alert.show();
OK, erstellen Sie eine  Layout Resource File:
  • File > New > Android Resource File
    • File Name: layout_custom_title.xml
    • Resource type: Layout
    • Directory name: layout
Dann entwerfen Sie die Interface für Title area:
layout_custom_title.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">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/icon_title" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:background="#E3DCC4"
        android:gravity="center"
        android:text="This is the Title"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView" />

</androidx.constraintlayout.widget.ConstraintLayout>
AlertDialogCustomTitleExample.java
package org.o7planning.alertdialogexample;

import android.app.Activity;
import android.content.Context;
import android.content.DialogInterface;
import android.graphics.drawable.Drawable;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Toast;

import androidx.appcompat.app.AlertDialog;

public class AlertDialogCustomTitleExample {

    public static void showAlertDialog(final Activity context)  {
        final Drawable positiveIcon = context.getResources().getDrawable(R.drawable.icon_positive);

        AlertDialog.Builder builder = new AlertDialog.Builder(context);

        // Custom Title Area.
        LayoutInflater inflater = context.getLayoutInflater();
        View view = inflater.inflate(R.layout.layout_custom_title, null);
        builder.setCustomTitle(view);

        // Message.
        builder.setMessage("This is AlertDialog with Custom Title Area");
        //
        builder.setCancelable(true);
        builder.setIcon(R.drawable.icon_title);

        // Create "OK" button with OnClickListener.
        builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
            }
        });
        builder.setPositiveButtonIcon(positiveIcon);

        // Create AlertDialog:
        AlertDialog alert = builder.create();
        alert.show();
    }
}

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