我对android developpement来说是全新的。我现在正试图做一个笔记应用程序。操作栏将有2个按钮，创建和设置，引导用户创建和设置页面。创建按钮工作得很好但我不知道为什么每当我运行应用程序并单击设置按钮它不会引导我到设置页面，应用程序突然停止。
这是我的代码
MainActivity.java
package com.example.sunny.mynote;
import android.app.ActionBar;
import android.app.ListActivity;
import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.ContextMenu;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Adapter;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import com.example.sunny.mynote.com.example.sunny.mynote.data.NoteDataSource;
import com.example.sunny.mynote.com.example.sunny.mynote.data.NoteItem;
import java.util.List;
public class MainActivity extends ListActivity {
public static final int EDITOR_ACRIVITY_REQUEST = 1001;
public static final int SETTINGS_REQUEST = 1003;
private static final int MENU_DELETE_ID = 1002;
private int currentNoteId;
private NoteDataSource datasource;
List<NoteItem> notesList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
registerForContextMenu(getListView());
datasource = new NoteDataSource(this);
refreshDisplay();
}
private void refreshDisplay() {
notesList = datasource.findAll();
ArrayAdapter<NoteItem> adapter =
new ArrayAdapter<NoteItem>(this, R.layout.list_item_layout, notesList);
setListAdapter(adapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId() == R.id.action_create)
{
createNote();
}
int id = item.getItemId();
if (id == R.id.action_create) {
return true;
}
if (item.getItemId() == R.id.action_settings)
{
Intent intent2 = new Intent(MainActivity.this, Settings.class);
startActivity(intent2);
}
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
private void createNote()
{
NoteItem note = NoteItem.getNew();
Intent intent = new Intent(this, NoteEditorActivity.class);
intent.putExtra("key", note.getKey());
intent.putExtra("text", note.getText());
startActivityForResult(intent, EDITOR_ACRIVITY_REQUEST);
}
private void Settings()
{
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
NoteItem note = notesList.get(position);
Intent intent = new Intent(this, NoteEditorActivity.class);
intent.putExtra("key", note.getKey());
intent.putExtra("text", note.getText());
startActivityForResult(intent, EDITOR_ACRIVITY_REQUEST);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == EDITOR_ACRIVITY_REQUEST && resultCode == RESULT_OK)
{
overridePendingTransition(R.anim.fadein, R.anim.fadeout);
NoteItem note = new NoteItem();
note.setKey(data.getStringExtra("key"));
note.setText(data.getStringExtra("text"));
datasource.update(note);
refreshDisplay();
}
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) menuInfo;
currentNoteId = (int)info.id;
menu.add(0, MENU_DELETE_ID, 0, "Delete");
}
@Override
public boolean onContextItemSelected(MenuItem item) {
if (item.getItemId() == MENU_DELETE_ID)
{
NoteItem note = notesList.get(currentNoteId);
datasource.remove(note);
refreshDisplay();
}
return super.onContextItemSelected(item);
}
}
Settings.java
package com.example.sunny.mynote;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Color;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.EditText;
/**
* Created by Sunny on 19/04/2015.
*/
public class Settings extends Activity {
View view = LayoutInflater.from(getApplication()).inflate(R.layout.activity_note_editor, null);
private RadioGroup RadioGroup1;
private RadioButton rdbRed, rdbBlue, rdbOrange;
private Button btnSave;
private TextView textView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.settings);
View view = LayoutInflater.from(getApplication()).inflate(R.layout.settings, null);
RadioGroup1 = (RadioGroup) findViewById(R.id.RadioGroup1);
RadioGroup1.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(RadioGroup group, int checkedId) {
if(checkedId == R.id.rdbRed)
{
Toast.makeText(getApplicationContext(), "choice: Red",
Toast.LENGTH_SHORT).show();
}
else if(checkedId == R.id.rdbBlue)
{
Toast.makeText(getApplicationContext(), "choice: Blue",
Toast.LENGTH_SHORT).show();
}
else
{
Toast.makeText(getApplicationContext(), "choice: Orange",
Toast.LENGTH_SHORT).show();
}
}
});
Intent intent = new Intent(this, NoteEditorActivity.class);
rdbRed = (RadioButton) findViewById(R.id.rdbRed);
rdbBlue = (RadioButton) findViewById(R.id.rdbBlue);
rdbOrange = (RadioButton) findViewById(R.id.rdbOrange);
textView = (TextView) findViewById(R.id.noteText);
btnSave = (Button)findViewById(R.id.btn_Save);
btnSave.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int selectedId = RadioGroup1.getCheckedRadioButtonId();
if(selectedId == rdbRed.getId()) {
textView.setTextColor(Color.parseColor("#FF0000"));
} else if(selectedId == rdbBlue.getId()) {
textView.setTextColor(Color.parseColor("#0066FF"));
} else {
textView.setTextColor(Color.parseColor("#FF6600"));
}
finish();
}
});
}
@Override
public void onBackPressed() {
finish();
}
}
日志
04-21 22:02:11.583 26636-26636/com.example.sunny.mynote I/SELinux﹕ Function: selinux_android_load_priority [0], There is no sepolicy file.
04-21 22:02:11.603 26636-26636/com.example.sunny.mynote I/SELinux﹕ Function: selinux_android_load_priority , spota verifySig and checkHash pass. priority version is VE=SEPF_SM-N9005_4.4.2_0040
04-21 22:02:11.603 26636-26636/com.example.sunny.mynote I/SELinux﹕ selinux_android_seapp_context_reload: seapp_contexts file is loaded from /data/security/spota/seapp_contexts
04-21 22:02:11.603 26636-26636/com.example.sunny.mynote E/dalvikvm﹕ >>>>> Normal User
04-21 22:02:11.603 26636-26636/com.example.sunny.mynote E/dalvikvm﹕ >>>>> com.example.sunny.mynote [ userId:0 | appId:10383 ]
04-21 22:02:11.603 26636-26636/com.example.sunny.mynote D/dalvikvm﹕ Late-enabling CheckJNI
04-21 22:02:11.613 26636-26636/com.example.sunny.mynote I/dalvikvm﹕ Enabling JNI app bug workarounds for target SDK version 7...
04-21 22:02:11.693 26636-26636/com.example.sunny.mynote W/ApplicationPackageManager﹕ getCSCPackageItemText()
04-21 22:02:11.693 26636-26636/com.example.sunny.mynote I/PersonaManager﹕ getPersonaService() name persona_policy
04-21 22:02:11.723 26636-26636/com.example.sunny.mynote E/MoreInfoHPW_ViewGroup﹕ Parent view is not a TextView
04-21 22:02:11.743 26636-26636/com.example.sunny.mynote D/AbsListView﹕ Get MotionRecognitionManager
04-21 22:02:11.763 26636-26636/com.example.sunny.mynote D/AbsListView﹕ onVisibilityChanged() is called, visibility : 4
04-21 22:02:11.763 26636-26636/com.example.sunny.mynote D/AbsListView﹕ unregisterIRListener() is called
04-21 22:02:11.763 26636-26636/com.example.sunny.mynote D/AbsListView﹕ onVisibilityChanged() is called, visibility : 0
04-21 22:02:11.763 26636-26636/com.example.sunny.mynote D/AbsListView﹕ unregisterIRListener() is called
04-21 22:02:11.773 26636-26636/com.example.sunny.mynote D/AbsListView﹕ unregisterIRListener() is called
04-21 22:02:11.793 26636-26636/com.example.sunny.mynote D/AbsListView﹕ unregisterIRListener() is called
04-21 22:02:11.793 26636-26636/com.example.sunny.mynote D/AbsListView﹕ unregisterIRListener() is called
04-21 22:02:11.823 26636-26636/com.example.sunny.mynote D/AbsListView﹕ unregisterIRListener() is called
04-21 22:02:12.868 26636-26636/com.example.sunny.mynote D/AbsListView﹕ Get MotionRecognitionManager
04-21 22:02:12.898 26636-26636/com.example.sunny.mynote D/AbsListView﹕ unregisterIRListener() is called
04-21 22:02:12.948 26636-26636/com.example.sunny.mynote D/AbsListView﹕ unregisterIRListener() is called
04-21 22:02:12.948 26636-26636/com.example.sunny.mynote D/AbsListView﹕ unregisterIRListener() is called
04-21 22:02:12.998 26636-26636/com.example.sunny.mynote D/AbsListView﹕ unregisterIRListener() is called
04-21 22:02:12.998 26636-26636/com.example.sunny.mynote D/AbsListView﹕ unregisterIRListener() is called
04-21 22:02:13.758 26636-26636/com.example.sunny.mynote D/AbsListView﹕ unregisterIRListener() is called
04-21 22:02:13.758 26636-26636/com.example.sunny.mynote D/AbsListView﹕ onDetachedFromWindow
04-21 22:02:13.758 26636-26636/com.example.sunny.mynote D/AbsListView﹕ unregisterIRListener() is called
04-21 22:02:13.758 26636-26636/com.example.sunny.mynote D/AndroidRuntime﹕ Shutting down VM
04-21 22:02:13.758 26636-26636/com.example.sunny.mynote W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x417e0da0)
04-21 22:02:13.768 26636-26636/com.example.sunny.mynote E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.sunny.mynote, PID: 26636
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.sunny.mynote/com.example.sunny.mynote.Settings}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2218)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2350)
at android.app.ActivityThread.access$800(ActivityThread.java:163)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1257)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:157)
at android.app.ActivityThread.main(ActivityThread.java:5335)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at android.view.LayoutInflater.from(LayoutInflater.java:212)
at com.example.sunny.mynote.Settings.<init>(Settings.java:21)
at java.lang.Class.newInstanceImpl(Native Method)
at java.lang.Class.newInstance(Class.java:1208)
at android.app.Instrumentation.newActivity(Instrumentation.java:1079)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2350)
at android.app.ActivityThread.access$800(ActivityThread.java:163)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1257)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:157)
at android.app.ActivityThread.main(ActivityThread.java:5335)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
at dalvik.system.NativeStart.main(Native Method)
04-21 22:02:15.248 26636-26636/com.example.sunny.mynote I/Process﹕ Sending signal. PID: 26636 S
IG：9
答案 0 :(得分：2)
尝试在“设置”中更改此行：
private View view;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.settings);
view = LayoutInflater.from(getApplication()).inflate(R.layout.activity_note_editor, null);
}
答案 1 :(得分：0)
你必须在内部膨胀视图或改变OnCreate（）的调用 所以在Settings.java
中的oncreate（）内移动你的行View view = LayoutInflater.from(getApplication()).inflate(R.layout.activity_note_editor, null);