Question

您好我正在尝试编写一个包含多个内容的Android应用。我有很多麻烦试图摆脱这种nullpoinerexception。当我点击应用程序中的按钮时，它会崩溃。有人可以帮忙吗？

MainActivity.java：

package com.smoke.rms;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {

 Button button1, button2;
 LinearLayout ourlayout;

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

  // Button1 = visit_our_site
  button1 = (Button) findViewById(R.id.button1);
  // Button2 = youtube_button
  button2 = (Button) findViewById(R.id.button2);

  // set onclick listeners for buttons
  button1.setOnClickListener(this);
  button2.setOnClickListener(this);

 }

 @Override
 public void onClick(View v) {
     Context context = null;

  switch (v.getId()) {

  case R.id.button1:
      Intent intent1 = new Intent(context, WebActivity.class);
      startActivity(intent1);
   break;

  case R.id.button2:
      Intent intent2 = new Intent(context, YouTubeActivity.class);
      startActivity(intent2);
   break;
  }
 }
// Initiating Menu XML file (menu.xml)
    public boolean onCreateOptionsMenu(Menu menu)
    {
        MenuInflater menuInflater = getMenuInflater();
        menuInflater.inflate(R.layout.menu, menu);
        return true;
    }
    public boolean onOptionsItemSelected(MenuItem item)
    {
        switch (item.getItemId())
        {
        case R.id.webView:
            Intent i = new Intent(Intent.ACTION_SEND);
            i.setType("message/rfc822");
            i.putExtra(Intent.EXTRA_EMAIL  , new String[]{"treavor.brown5875@gmail.com"});
            try {
                startActivity(Intent.createChooser(i, "Send mail..."));
            } catch (android.content.ActivityNotFoundException ex) {
                Toast.makeText(MainActivity.this, "There are no email clients installed.", Toast.LENGTH_SHORT).show();
            }
        }
        return false;
    }
    }

main.xml中：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/button1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/visit_our_site" />

    <Button
        android:id="@+id/button2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/youtube" />

</LinearLayout>

Answer 1

唔。按钮单击中显示Context context = null ....显然这是问题

Answer 2

我认为你的错误来自第39行

Context context = null;

你应该删除这一行和

使用

实现您的意图

Intent intent1 = new Intent(MainActivity.this, WebActivity.class); startActivity(intent1);

你应该对意图2

一样

我得到了一个无法修复的nullpointerexception

2 个答案: