当我启动应用程序时 MainActivity 成功启动但是当我在文本编辑字段中插入文本并按下按钮时应用程序崩溃
Android 清单文件
<uses-sdk
android:minSdkVersion="10"
android:targetSdkVersion="10" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.sateesh.explicit_intents.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name= "com.sateesh.explicit_intents.Second"
android:label="@string/app_name">
</activity>
</application>
</manifest>
这是 Main_Activity：
package com.sateesh.explicit_intents;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Refernce of UI objects
final EditText et=(EditText)findViewById(R.id.editText1);
Button b =(Button) findViewById(R.id.button1);
b.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Intent i= new Intent(MainActivity.this, Second.class);
// Getting
i.putExtra("thetext", et.getText().toString());
startActivity(i);
}
});
}
@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;
}
}
main_activity.xml：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<EditText
android:id="@+id/editText1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:ems="10" />
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/editText1"
android:layout_below="@+id/editText1"
android:text="Go To Second Activity" />
</RelativeLayout>
第二个活动：
package com.sateesh.explicit_intents;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
public class Second extends Activity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView tv=(TextView)findViewById(R.id.textView1);
tv.setText(getIntent().getExtras().getString("thetext"));
}
}
第二个.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
</LinearLayout>
当我尝试在模拟器上运行它时。MainActivity 成功启动。但是，当我插入文本并按下按钮时，程序崩溃并出现以下错误。
10-28 00:43:16.692: D/gralloc_goldfish(2002): Emulator without GPU emulation detected.
10-28 00:43:17.462: W/KeyCharacterMap(2002): No keyboard for id 0
10-28 00:43:17.462: W/KeyCharacterMap(2002): Using default keymap: /system/usr/keychars/qwerty.kcm.bin
10-28 00:43:18.393: D/AndroidRuntime(2002): Shutting down VM
10-28 00:43:18.393: W/dalvikvm(2002): threadid=1: thread exiting with uncaught exception (group=0xb6f794f0)
10-28 00:43:18.433: E/AndroidRuntime(2002): FATAL EXCEPTION: main
10-28 00:43:18.433: E/AndroidRuntime(2002): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sateesh.explicit_intents/com.sateesh.explicit_intents.Second}: java.lang.NullPointerException
10-28 00:43:18.433: E/AndroidRuntime(2002): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
10-28 00:43:18.433: E/AndroidRuntime(2002): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
10-28 00:43:18.433: E/AndroidRuntime(2002): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
10-28 00:43:18.433: E/AndroidRuntime(2002): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
10-28 00:43:18.433: E/AndroidRuntime(2002): at android.os.Handler.dispatchMessage(Handler.java:99)
10-28 00:43:18.433: E/AndroidRuntime(2002): at android.os.Looper.loop(Looper.java:130)
10-28 00:43:18.433: E/AndroidRuntime(2002): at android.app.ActivityThread.main(ActivityThread.java:3683)
10-28 00:43:18.433: E/AndroidRuntime(2002): at java.lang.reflect.Method.invokeNative(Native Method)
10-28 00:43:18.433: E/AndroidRuntime(2002): at java.lang.reflect.Method.invoke(Method.java:507)
10-28 00:43:18.433: E/AndroidRuntime(2002): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
10-28 00:43:18.433: E/AndroidRuntime(2002): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
10-28 00:43:18.433: E/AndroidRuntime(2002): at dalvik.system.NativeStart.main(Native Method)
10-28 00:43:18.433: E/AndroidRuntime(2002): Caused by: java.lang.NullPointerException
10-28 00:43:18.433: E/AndroidRuntime(2002): at com.sateesh.explicit_intents.Second.onCreate(Second.java:14)
10-28 00:43:18.433: E/AndroidRuntime(2002): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-28 00:43:18.433: E/AndroidRuntime(2002): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
10-28 00:43:18.433: E/AndroidRuntime(2002): ... 11 more
10-28 00:43:20.711: I/Process(2002): Sending signal. PID: 2002 SIG: 9
当我启动应用程序时 MainActivity 成功启动，但是当我在文本编辑字段中插入文本并按下按钮时应用程序崩溃。