Question

我是android学习的新手。使用Android Studio。我的应用名称是Design1。我正在学习活动，所以创建了一个活动页面，其中有两个用于测试两个事件的按钮，一个是toast，另一个是Alert dialog box。吐司工作正常，但是当我点击ALERT按钮显示警报对话框然后出现一条消息，即“ Design1已停止”。

如果我从activity_events.xml和events.java文件中删除showAlert事件，那么我的工作就完美了。

events.java

package com.example.borntoflirt.design1;

import android.app.Dialog;
import android.content.DialogInterface;
import android.content.Context;
import android.content.pm.PackageManager;
import android.graphics.Camera;
import android.hardware.camera2.CameraManager;
import android.os.Build;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class events extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_events);
}

public void showToast(View v) {
    Context context = getApplicationContext();  // OR getBaseContext()
    CharSequence text = "Hi Toast";
    int duration = Toast.LENGTH_SHORT;

    Toast toast = Toast.makeText(context, text, duration);
    toast.show();
}

public void showAlert(View v) {
    Context context1 = getApplicationContext();
    AlertDialog.Builder builder = new AlertDialog.Builder(context1);
    builder.setMessage("Write your message here.");
    builder.setCancelable(true);

    builder.setPositiveButton(
            "Yes",
            new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int id) {
                    dialog.cancel();
                }
            });

    builder.setNegativeButton(
            "No",
            new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int id) {
                    dialog.cancel();
                }
            });

    AlertDialog alert = builder.create();
    alert.show();
}

}

activity_events.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/holo_red_light"
android:isScrollContainer="false"
android:orientation="vertical"
android:paddingLeft="15dp"
android:paddingRight="15dp">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal">

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_margin="2dp"
        android:layout_weight=".30"
        android:background="@drawable/rounded_button"
        android:text="Toast"
        android:textColor="#000"
        android:onClick="showToast"/>

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight=".30"
        android:text="Alert"
        android:textColor="#000"
        android:background="@drawable/rounded_button"
        android:layout_margin="2dp"
        android:onClick="showAlert"/>

</LinearLayout>

</LinearLayout>

Answer 1

您需要使用活动上下文。如果您使用应用程序上下文，则将抛出IllegalStateExpetion。

<!DOCTYPE html>
<html>
<head>

   <!-- Latest compiled and minified CSS -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">

<!-- jQuery library -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
  <link rel="stylesheet" href="style.css">
    <link href="https://fonts.googleapis.com/css?family=Roboto" rel="stylesheet">
<!-- Latest compiled JavaScript -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>

    <body>
    <div class="header">
        <div class="header-text">100+ Years Of Combiend Industry Expierence</div>

<div class="header-logo"></div>                   

        </div>

    </body>
</html>

Answer 2

使用活动的背景：

AlertDialog.Builder builder = new AlertDialog.Builder(event.this);

取代

 Context context1 = getApplicationContext();
AlertDialog.Builder builder = new AlertDialog.Builder(context1);

Answer 3

尝试使用getActivity()代替getApplicationContext()。

Answer 4

已经7个月了，但是没有一个答案对我有用。所以这是我找到的解决方案。尝试使用select * from tasks where initialPrice > 20 and case when status = 3 Then 1 when status in (1,5) and userId = 5 Then 1 else 0 end = 1而不是MainActivity.this或getApplicationContext()。

Android工作室APP已停止

4 个答案: