Question

我的Android应用程序存在问题，我试图做的是按下ToggleButton，应用程序每两秒写一次文件Hello（我真正想要的是保存在每隔2秒发送一次gps位置），ToggleButton具有id：boto1。

这是MainActivity.java：

package com.example.gasquefabaixada;

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.ToggleButton;


public class MainActivity extends ActionBarActivity {

    private ToggleButton Boto1;
    @Override



    protected void onCreate(Bundle savedInstanceState) {

        ToggleButton bt = (ToggleButton) findViewById(R.id.boto1);
        bt.setOnCheckedChangeListener(new OnCheckedChangeListener() {

            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

                if(isChecked)
                {
                    BufferedWriter writer = null;
                    try {
                        writer = new BufferedWriter(new FileWriter("mnt/sdcard/andromina.txt"));
                    } catch (IOException e1) {
                        // TODO Auto-generated catch block
                        e1.printStackTrace();
                    }
                    while(isChecked==true)
                    {


                        Thread.currentThread();
                        try {

                            writer.write("HELLO");
                            writer.newLine();
                            Thread.sleep(2000);
                        } catch (InterruptedException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        } catch (IOException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                    }
                    try {
                        writer.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
                else
                {

                }

            }
        });

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
     //   Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

程序崩溃!!!

谢谢大家!!

Answer 1

我很确定你有一个NullPointerException，所以在onCreate()方法之后添加两行

 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);

然后您的代码会在boto1布局

中找到元素activity_main

  ToggleButton bt = (ToggleButton) findViewById(R.id.boto1);

Answer 2

您必须在onCreate()

的开头提供这两行

super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

同样，您确定ToggleButton位于activity_main.xml。检查它是否在fragment_main.xml ..如果它在fragment_main.xml，您肯定会得到NullPointerException。

在扩展ActionBarActivity时，正确的做法是使用onCreateView()来扩充视图，并且UI元素应放在片段内（例如.fragment_main.xml）。在您的代码中，您正在执行此操作在onCreate()本身。

所以你的onCreateView()应该是

public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View view=inflater.inflate(R.layout.fragment_main.xml, null);
    ToggleButton bt = (ToggleButton) findViewById(R.id.boto1);
    bt.setOnCheckedChangeListener(new OnCheckedChangeListener() {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

            if(isChecked)
            {
                BufferedWriter writer = null;
                try {
                    writer = new BufferedWriter(new FileWriter("mnt/sdcard/andromina.txt"));
                } catch (IOException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
                while(isChecked==true)
                {


                    Thread.currentThread();
                    try {

                        writer.write("HELLO");
                        writer.newLine();
                        Thread.sleep(2000);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
                try {
                    writer.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            else
            {

            }

        }
    });
    return view;
}

并从onCreate()

中删除这些行

Answer 3

您在致电findViewById(R.id.boto1)之前致电setContentView(R.layout.activity_main)，以便无法找到该视图。我认为崩溃可能是NullPointerException，因为ToggleButton bt绝对是空的，因为任何布局或视图都已设置。：）

试试这个：

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    ToggleButton bt = (ToggleButton) findViewById(R.id.boto1);
    bt.setOnCheckedChangeListener(new OnCheckedChangeListener() {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

            if(isChecked) {
                ...
            } else {
                ...
            }
        }
    });
}

MainActivity.java中的问题尝试使用ToogleButton

3 个答案: