空指针异常

q5661889 2014-11-13 11:39:12
这是短信接收类:
package com.example.bluetooth___watch;



import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.telephony.SmsMessage;
import android.widget.Toast;

public class SMSReceiver extends BroadcastReceiver {
/* 当收到短信时,就会触发此方法 */
public void onReceive(Context context, Intent intent) {
Bundle bundle = intent.getExtras();
Object messages[] = (Object[]) bundle.get("pdus");
SmsMessage smsMessage[] = new SmsMessage[messages.length];
for (int n = 0; n < messages.length; n++) {
smsMessage[n] = SmsMessage.createFromPdu((byte[]) messages[n]);
}
// 产生一个Toast
Toast toast = Toast.makeText(context,
"短信内容: " + smsMessage[0].getMessageBody(), Toast.LENGTH_LONG);
// 设置toast显示的位置
// toast.setGravity(Gravity.TOP|Gravity.LEFT, 0, 200);
// 显示该Toast
toast.show();

//调用显示短信内容的Activity

Intent in = new Intent();
in.setClass(context, MainActivity.class);
in.putExtra("message", smsMessage[0].getMessageBody());
context.startActivity(in);
}

}


这是主类:

package com.example.bluetooth___watch;

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.content.Intent;
import android.os.Bundle;
import android.view.Gravity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity {
String username ;
/* 取得默认的蓝牙适配器 */
private BluetoothAdapter _bluetooth = BluetoothAdapter.getDefaultAdapter();

/* 请求打开蓝牙 */
private static final int REQUEST_ENABLE = 0x1;
/* 请求能够被搜索 */
private static final int REQUEST_DISCOVERABLE = 0x2;

Button Button1, Button2, Button3,Button4;

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

Button1 = (Button) findViewById(R.id.open_bluetooth);
Button2 = (Button) findViewById(R.id.Can_be_searched);
Button3 = (Button) findViewById(R.id.search_device);
Button4 = (Button) findViewById(R.id.Show_Message);
// 设置按钮1的事件监听
Button1.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
// 用户请求打开蓝牙
// Intent enabler = new
// Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
// startActivityForResult(enabler, REQUEST_ENABLE);
// 打开蓝牙
_bluetooth.enable();
}
});

// 设置按钮2的事件监听
Button2.setOnClickListener(new Button.OnClickListener() {
/* 使设备能够被搜索 */
public void onClick(View v)

{

Intent enabler = new Intent(
BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
startActivityForResult(enabler, REQUEST_DISCOVERABLE);
}
});

// 设置按钮3的事件监听
Button3.setOnClickListener(new Button.OnClickListener() {
/* 开始搜索 */
public void onClick(View v)

{

Intent enabler = new Intent(MainActivity.this,
DiscoveryActivity.class);
startActivity(enabler);
}

});

Bundle bu = this.getIntent().getExtras();
username = bu.getString("message");//获取短信内容
/*
// 设置按钮4的事件信息 */
Button4.setOnClickListener(new Button.OnClickListener() {

public void onClick(View v)
{



DisplayToast(username);
}
});

}



/* 显示Toast */
public void DisplayToast(String str) {
Toast.makeText(this, str, Toast.LENGTH_SHORT).show();
}
}


报错信息:
11-13 10:49:24.180: D/AndroidRuntime(11931): Shutting down VM
11-13 10:49:24.180: W/dalvikvm(11931): threadid=1: thread exiting with uncaught exception (group=0x420112b8)
11-13 10:49:24.180: E/AndroidRuntime(11931): FATAL EXCEPTION: main
11-13 10:49:24.180: E/AndroidRuntime(11931): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.bluetooth___watch/com.example.bluetooth___watch.MainActivity}: java.lang.NullPointerException
11-13 10:49:24.180: E/AndroidRuntime(11931): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2118)
11-13 10:49:24.180: E/AndroidRuntime(11931): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2143)
11-13 10:49:24.180: E/AndroidRuntime(11931): at android.app.ActivityThread.access$700(ActivityThread.java:140)
11-13 10:49:24.180: E/AndroidRuntime(11931): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1237)
11-13 10:49:24.180: E/AndroidRuntime(11931): at android.os.Handler.dispatchMessage(Handler.java:99)
11-13 10:49:24.180: E/AndroidRuntime(11931): at android.os.Looper.loop(Looper.java:137)
11-13 10:49:24.180: E/AndroidRuntime(11931): at android.app.ActivityThread.main(ActivityThread.java:4952)
11-13 10:49:24.180: E/AndroidRuntime(11931): at java.lang.reflect.Method.invokeNative(Native Method)
11-13 10:49:24.180: E/AndroidRuntime(11931): at java.lang.reflect.Method.invoke(Method.java:511)
11-13 10:49:24.180: E/AndroidRuntime(11931): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
11-13 10:49:24.180: E/AndroidRuntime(11931): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
11-13 10:49:24.180: E/AndroidRuntime(11931): at dalvik.system.NativeStart.main(Native Method)
11-13 10:49:24.180: E/AndroidRuntime(11931): Caused by: java.lang.NullPointerException
11-13 10:49:24.180: E/AndroidRuntime(11931): at com.example.bluetooth___watch.MainActivity.onCreate(MainActivity.java:61)
11-13 10:49:24.180: E/AndroidRuntime(11931): at android.app.Activity.performCreate(Activity.java:5188)
11-13 10:49:24.180: E/AndroidRuntime(11931): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
11-13 10:49:24.180: E/AndroidRuntime(11931): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2082)
11-13 10:49:24.180: E/AndroidRuntime(11931): ... 11 more
11-13 10:54:30.160: I/Process(11931): Sending signal. PID: 11931 SIG: 9
...全文
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红袖满楼招 2014-11-14
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11-13 10:49:24.180: E/AndroidRuntime(11931): at com.example.bluetooth___watch.MainActivity.onCreate(MainActivity.java:61)
answer艾 2014-11-13
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你在有数据产生的地方 放logcat 显示出来 你看看你自己哪个数据没有应用到就知道了
heaven_wsh 2014-11-13
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11-13 10:49:24.180: E/AndroidRuntime(11931): Caused by: java.lang.NullPointerException 11-13 10:49:24.180: E/AndroidRuntime(11931): at com.example.bluetooth___watch.MainActivity.onCreate(MainActivity.java:61) 显示61行有空指针,你贴出来的代码和你出错时候的代码是一个版本吗

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