无法启动ComponentInfo显示java.lang.NullPointerException [英] Unable to start ComponentInfo java.lang.NullPointerException
问题描述
我得到一个显示java.lang.NullPointerException错误,我不知道为什么。我想这可能是与有如何在我的数据库没有数据,但我不知道肯定。有没有人对如何使我的数据库接受那里是没有数据有什么建议?我已经采取了code&放;在多个网站/书籍这个研究,但是这是我得到和我仍然得到错误最接近的!帮助是极大的AP preciated!谢谢你在前进!
logcat的:
一月9日至27日:17:14.656:E / AndroidRuntime(3331):致命异常:主要
一月9日至27日:17:14.656:E / AndroidRuntime(3331):了java.lang.RuntimeException:无法启动活动ComponentInfo {com.pocketbotanist / com.pocketbotanist.HomeScreen}:显示java.lang.NullPointerException
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2247)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2297)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在android.app.ActivityThread.access $ 700(ActivityThread.java:152)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1282)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在android.os.Handler.dispatchMessage(Handler.java:99)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在android.os.Looper.loop(Looper.java:137)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在android.app.ActivityThread.main(ActivityThread.java:5328)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在java.lang.reflect.Method.invokeNative(本机方法)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在java.lang.reflect.Method.invoke(Method.java:511)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:1102)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在dalvik.system.NativeStart.main(本机方法)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):因:显示java.lang.NullPointerException
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在com.pocketbotanist.HomeScreen.onCreate(HomeScreen.java:69)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在android.app.Activity.performCreate(Activity.java:5250)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1097)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
一月9日至27日:17:14.656:E / AndroidRuntime(3331):11 ...更多
code:
包com.pocketbotanist;进口的java.io.File;进口android.app.ListActivity;
进口android.app.LoaderManager;
进口android.content.CursorLoader;
进口android.content.Intent;
进口android.content.Loader;
进口android.content.pm.ActivityInfo;
进口android.content.res.Configuration;
进口android.database.Cursor;
进口android.net.Uri;
进口android.os.Bundle;
进口android.os.Environment;
进口android.view.ContextMenu;
进口android.view.ContextMenu.ContextMenuInfo;
进口android.view.Menu;
进口android.view.MenuItem;
进口android.view.View;
进口android.widget.AdapterView.AdapterContextMenuInfo;
进口android.widget.ArrayAdapter;
进口android.widget.ListView;
进口android.widget.SimpleCursorAdapter;
进口android.widget.Spinner;进口com.pocketbotanist.contentprovider.MyEntryContentProvider;
进口com.pocketbotanist.database.EntryTable;公共类主屏幕扩展ListActivity实现LoaderManager.LoaderCallbacks<&光标GT; { 私有静态最终诠释DELETE_ID = Menu.FIRST + 1;
//私人光标指针;
私人SimpleCursorAdapter适配器; @覆盖
保护无效的onCreate(捆绑savedInstanceState){
super.onCreate(savedInstanceState);
的setContentView(R.layout.activity_home_screen);
this.getListView()setDividerHeight(2)。
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT); //初始文件夹创建code
文件appDirectory =新的文件(Environment.getExternalStorageDirectory()的toString()+/掌上植物学/);
如果(!appDirectory.exists()){
appDirectory.mkdir();
} //下拉列表code
微调微调=(微调)findViewById(R.id.action_spinner);
ArrayAdapter<&CharSequence的GT;适配器= ArrayAdapter.createFromResource(这一点,R.array.action_list,android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(适配器);
fillData();
@燮pressWarnings(未使用)
查看查看=(查看)getListView()getItemAtPosition(0);
registerForContextMenu(getListView());
如果(adapter.isEmpty())
的System.out.println(是空);
的String [] =投影{EntryTable.COLUMN_CUSTOMID};
长信息= adapter.getItemId(0);
URI URI = Uri.parse(MyEntryContentProvider.CONTENT_URI +/
+信息);
光标光标= getContentResolver()查询(URI,投影,NULL,NULL,NULL);
cursor.moveToFirst();
的System.out.println((cursor.getString(光标
.getColumnIndexOrThrow(EntryTable.COLUMN_CUSTOMID))));
} @覆盖
公共无效onConfigurationChanged(配置NEWCONFIG){
super.onConfigurationChanged(NEWCONFIG);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
}
@覆盖
公共布尔onContextItemSelected(菜单项项){
开关(item.getItemId()){
案例DELETE_ID:
的String [] =投影{EntryTable.COLUMN_PHOTOS};
AdapterContextMenuInfo信息=(AdapterContextMenuInfo)项目
.getMenuInfo();
URI URI = Uri.parse(MyEntryContentProvider.CONTENT_URI +/
+ info.id);
光标光标= getContentResolver()查询(URI,投影,NULL,NULL,NULL);
cursor.moveToFirst();
文件临时=新的文件(cursor.getString(光标
.getColumnIndexOrThrow(EntryTable.COLUMN_PHOTOS)));
如果(temp.exists()){
文件[] =文件temp.listFiles();
的for(int i = 0; I< files.length;我++){
文件[I] .delete();
}
temp.delete();
}
。getContentResolver()删除(URI,NULL,NULL);
fillData();
返回true;
} 返回super.onContextItemSelected(项目); }
@覆盖
公共布尔onCreateOptionsMenu(菜单菜单){
//充气菜单;如果是present这增加了项目操作栏。
。getMenuInflater()膨胀(R.menu.activity_home_screen,菜单);
//搜索查看搜索查看=(搜索查看)menu.findItem(R.id.menu_search).getActionView();
返回true;
} @覆盖
公共布尔onOptionsItemSelected(菜单项项){
//处理项目选择
开关(item.getItemId()){
案例R.id.menu_settings:
settCall();
返回true;
案例R.id.menu_map:
map1_3();
返回true;
案例R.id.menu_edit:
entryScreen(新建项目);
返回true;
默认:
返回super.onOptionsItemSelected(项目);
}
} 公共无效entryScreen(串T){
意向意图=新意图(这一点,EntryScreen.class);
intent.putExtra(过客,T);
startActivity(意向);
} 公共无效settCall(){
意图SETT =新意图(这一点,SettingsActivity.class);
startActivity(SETT);
} 公共无效map1_3(){ 意图map13 =新意图(这一点,Entrymap_1_3.class);
startActivity(map13);
}
//打开第二个活动如果点击一个条目
@覆盖
保护无效onListItemClick(ListView中升,视图V,INT位置,长的id){
super.onListItemClick(L,V,位置ID);
意图I =新意图(这一点,EntryScreen.class);
乌里itemUri = Uri.parse(MyEntryContentProvider.CONTENT_URI +/+ ID);
i.putExtra(MyEntryContentProvider.CONTENT_ITEM_TYPE,itemUri); startActivity(ⅰ);
} // @覆盖
//当我们创建我们会得到投影的ID,customID,品种名称和时间列装载机
//(保证了这些存在的数据库内)
//然后我们创建光标器会负责从数据库中装载数据
使用投影和我们的内容提供商//
公共装载机<&光标GT; onCreateLoader(INT为arg0,ARG1捆绑){
的String [] =投影{EntryTable.COLUMN_ID,EntryTable.COLUMN_CUSTOMID,EntryTable.COLUMN_SPECIES,EntryTable.COLUMN_TIME,EntryTable.COLUMN_PHOTOS,EntryTable.COLUMN_PHOTO};
CursorLoader cursorLoader =新CursorLoader(这一点,
MyEntryContentProvider.CONTENT_URI,投影,NULL,NULL,NULL);
返回cursorLoader;
} 私人无效fillData(){ //字段从数据库(凸起)
的String [] =由新的String [] {EntryTable.COLUMN_CUSTOMID,EntryTable.COLUMN_SPECIES,EntryTable.COLUMN_TIME,EntryTable.COLUMN_PHOTO};
//领域上,我们的地图UI
INT []为= INT新[] {R.id.customidlabel,R.id.namelabel,R.id.timelabel,R.id.imageView}; getLoaderManager()initLoader(1,null,则此)。 //改为1
适配器=新SimpleCursorAdapter(这一点,R.layout.list_row,空,发件人,收件人,0); setListAdapter(适配器);
} @覆盖
公共无效onCreateContextMenu(文本菜单菜单视图V,ContextMenuInfo menuInfo){
super.onCreateContextMenu(菜单,V,menuInfo);
menu.add(0,DELETE_ID,0,R.string.menu_delete);
}
@覆盖
公共无效onLoadFinished(装载机<&光标GT;为arg0,游标数据){
adapter.swapCursor(数据);
} @覆盖
公共无效onLoaderReset(装载机<&光标GT;为arg0){
adapter.swapCursor(NULL);
}}
这是返回null的查询方法,你的光标为null:
光标光标= getContentResolver()查询(URI,投影,NULL,NULL,NULL); //检查为什么你的查询返回null
cursor.moveToFirst(); //光标为null
I am getting a java.lang.NullPointerException error, and am not sure why. I think it could have something to do with how there is no data in my database, but I don't know for certain. Does anyone have any suggestions on how to make my database accept there being no data? I've taken code & researched this on multiple websites/books, but this is the closest I have gotten and am still getting errors! Help is greatly appreciated! Thank you in advance!
Logcat:
09-27 01:17:14.656: E/AndroidRuntime(3331): FATAL EXCEPTION: main
09-27 01:17:14.656: E/AndroidRuntime(3331): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.pocketbotanist/com.pocketbotanist.HomeScreen}: java.lang.NullPointerException
09-27 01:17:14.656: E/AndroidRuntime(3331): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2247)
09-27 01:17:14.656: E/AndroidRuntime(3331): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2297)
09-27 01:17:14.656: E/AndroidRuntime(3331): at android.app.ActivityThread.access$700(ActivityThread.java:152)
09-27 01:17:14.656: E/AndroidRuntime(3331): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1282)
09-27 01:17:14.656: E/AndroidRuntime(3331): at android.os.Handler.dispatchMessage(Handler.java:99)
09-27 01:17:14.656: E/AndroidRuntime(3331): at android.os.Looper.loop(Looper.java:137)
09-27 01:17:14.656: E/AndroidRuntime(3331): at android.app.ActivityThread.main(ActivityThread.java:5328)
09-27 01:17:14.656: E/AndroidRuntime(3331): at java.lang.reflect.Method.invokeNative(Native Method)
09-27 01:17:14.656: E/AndroidRuntime(3331): at java.lang.reflect.Method.invoke(Method.java:511)
09-27 01:17:14.656: E/AndroidRuntime(3331): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
09-27 01:17:14.656: E/AndroidRuntime(3331): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
09-27 01:17:14.656: E/AndroidRuntime(3331): at dalvik.system.NativeStart.main(Native Method)
09-27 01:17:14.656: E/AndroidRuntime(3331): Caused by: java.lang.NullPointerException
09-27 01:17:14.656: E/AndroidRuntime(3331): at com.pocketbotanist.HomeScreen.onCreate(HomeScreen.java:69)
09-27 01:17:14.656: E/AndroidRuntime(3331): at android.app.Activity.performCreate(Activity.java:5250)
09-27 01:17:14.656: E/AndroidRuntime(3331): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1097)
09-27 01:17:14.656: E/AndroidRuntime(3331): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
09-27 01:17:14.656: E/AndroidRuntime(3331): ... 11 more
Code:
package com.pocketbotanist;
import java.io.File;
import android.app.ListActivity;
import android.app.LoaderManager;
import android.content.CursorLoader;
import android.content.Intent;
import android.content.Loader;
import android.content.pm.ActivityInfo;
import android.content.res.Configuration;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView.AdapterContextMenuInfo;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.Spinner;
import com.pocketbotanist.contentprovider.MyEntryContentProvider;
import com.pocketbotanist.database.EntryTable;
public class HomeScreen extends ListActivity implements LoaderManager.LoaderCallbacks<Cursor> {
private static final int DELETE_ID = Menu.FIRST + 1;
// private Cursor cursor;
private SimpleCursorAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home_screen);
this.getListView().setDividerHeight(2);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
//Initial folder creation code
File appDirectory = new File(Environment.getExternalStorageDirectory().toString()+"/Pocket Botanist/");
if (!appDirectory.exists()){
appDirectory.mkdir();
}
//Drop down list code
Spinner spinner = (Spinner) findViewById(R.id.action_spinner);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.action_list, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
fillData();
@SuppressWarnings("unused")
View view = (View) getListView().getItemAtPosition(0);
registerForContextMenu(getListView());
if (adapter.isEmpty())
System.out.println("IT'S EMPTY");
String[] projection = { EntryTable.COLUMN_CUSTOMID };
long info = adapter.getItemId(0);
Uri uri = Uri.parse(MyEntryContentProvider.CONTENT_URI + "/"
+ info);
Cursor cursor = getContentResolver().query(uri, projection, null, null, null);
cursor.moveToFirst();
System.out.println((cursor.getString(cursor
.getColumnIndexOrThrow(EntryTable.COLUMN_CUSTOMID))));
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
}
@Override
public boolean onContextItemSelected(MenuItem item) {
switch (item.getItemId()) {
case DELETE_ID:
String[] projection = { EntryTable.COLUMN_PHOTOS };
AdapterContextMenuInfo info = (AdapterContextMenuInfo) item
.getMenuInfo();
Uri uri = Uri.parse(MyEntryContentProvider.CONTENT_URI + "/"
+ info.id);
Cursor cursor = getContentResolver().query(uri, projection, null, null, null);
cursor.moveToFirst();
File temp = new File(cursor.getString(cursor
.getColumnIndexOrThrow(EntryTable.COLUMN_PHOTOS)));
if(temp.exists()){
File[] files = temp.listFiles();
for(int i = 0; i < files.length; i++){
files[i].delete();
}
temp.delete();
}
getContentResolver().delete(uri, null, null);
fillData();
return true;
}
return super.onContextItemSelected(item);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_home_screen, menu);
//SearchView searchView = (SearchView) menu.findItem(R.id.menu_search).getActionView();
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
switch (item.getItemId()) {
case R.id.menu_settings:
settCall();
return true;
case R.id.menu_map:
map1_3();
return true;
case R.id.menu_edit:
entryScreen("New Entry");
return true;
default:
return super.onOptionsItemSelected(item);
}
}
public void entryScreen(String t){
Intent intent = new Intent(this, EntryScreen.class);
intent.putExtra("passer", t);
startActivity(intent);
}
public void settCall(){
Intent sett = new Intent(this,SettingsActivity.class);
startActivity(sett);
}
public void map1_3(){
Intent map13 = new Intent(this,Entrymap_1_3.class);
startActivity(map13);
}
// Opens the second activity if an entry is clicked
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
Intent i = new Intent(this, EntryScreen.class);
Uri itemUri = Uri.parse(MyEntryContentProvider.CONTENT_URI + "/" + id);
i.putExtra(MyEntryContentProvider.CONTENT_ITEM_TYPE, itemUri);
startActivity(i);
}
//@Override
//When we create the loader we're going to get the projection for the ID, customID, species name, and time columns
//(insures that these exist within the database)
//then we create our cursor loader which will be responsible for loading data from the database
//using the projection and our content provider
public Loader<Cursor> onCreateLoader(int arg0, Bundle arg1) {
String[] projection = { EntryTable.COLUMN_ID, EntryTable.COLUMN_CUSTOMID, EntryTable.COLUMN_SPECIES, EntryTable.COLUMN_TIME, EntryTable.COLUMN_PHOTOS, EntryTable.COLUMN_PHOTO };
CursorLoader cursorLoader = new CursorLoader(this,
MyEntryContentProvider.CONTENT_URI, projection, null, null, null);
return cursorLoader;
}
private void fillData() {
// Fields from the database (projection)
String[] from = new String[] { EntryTable.COLUMN_CUSTOMID, EntryTable.COLUMN_SPECIES , EntryTable.COLUMN_TIME, EntryTable.COLUMN_PHOTO};
// Fields on the UI to which we map
int[] to = new int[] { R.id.customidlabel, R.id.namelabel, R.id.timelabel, R.id.imageView };
getLoaderManager().initLoader(1, null, this); //changed to 1
adapter = new SimpleCursorAdapter(this, R.layout.list_row, null, from, to, 0);
setListAdapter(adapter);
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
super.onCreateContextMenu(menu, v, menuInfo);
menu.add(0, DELETE_ID, 0, R.string.menu_delete);
}
@Override
public void onLoadFinished(Loader<Cursor> arg0, Cursor data) {
adapter.swapCursor(data);
}
@Override
public void onLoaderReset(Loader<Cursor> arg0) {
adapter.swapCursor(null);
}
}
It's the query method that returns null, your cursor is null :
Cursor cursor = getContentResolver().query(uri, projection, null, null, null);// check why your query is returning null
cursor.moveToFirst(); // cursor is null
这篇关于无法启动ComponentInfo显示java.lang.NullPointerException的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!