我正在尝试创建和使用动态标签但是如果我使用切换，添加或删除标签ONCE应用程序正常工作，但一旦我尝试选择第二个操作应用程序崩溃。我知道问题在于标签代码，因为应用程序在标签部分
之前工作正常这是我的MainActivity.java：
package com.example.notepadxl;
import java.io.*;
import android.os.*;
import android.annotation.SuppressLint;
import android.annotation.TargetApi;
import android.app.*;
import android.app.ActionBar.Tab;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
//import android.content.pm.PackageManager;
import android.graphics.Typeface;
import android.view.*;
import android.widget.*;
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
@SuppressLint("WorldReadableFiles")
public class MainActivity extends Activity {
Typeface tf=Typeface.SERIF;
int sty=Typeface.NORMAL;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void onAddTab() {
final ActionBar bar = getActionBar();
final int tabCount = bar.getTabCount();
final String text = "Tab " + tabCount;
bar.addTab(bar.newTab()
.setText(text)
.setTabListener(new TabListener(new TabContentFragment(text))));
}
public void onRemoveTab() {
final ActionBar bar = getActionBar();
if(bar.getTabCount() > 0)
bar.removeTabAt(bar.getTabCount() - 1);
}
public void onToggleTabs() {
final ActionBar bar = getActionBar();
if (bar.getNavigationMode() == ActionBar.NAVIGATION_MODE_TABS) {
bar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
bar.setDisplayOptions(ActionBar.DISPLAY_SHOW_TITLE, ActionBar.DISPLAY_SHOW_TITLE);
} else {
bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
bar.setDisplayOptions(0, ActionBar.DISPLAY_SHOW_TITLE);
}
}
public void onRemoveAllTabs(View v) {
getActionBar().removeAllTabs();
}
private class TabListener implements ActionBar.TabListener {
private TabContentFragment mFragment;
public TabListener(TabContentFragment fragment) {
mFragment = fragment;
}
public void onTabSelected(Tab tab, FragmentTransaction ft) {
ft.add(R.id.fragment_content, mFragment, mFragment.getText());
}
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
ft.remove(mFragment);
}
public void onTabReselected(Tab tab, FragmentTransaction ft) {
Toast.makeText(MainActivity.this, "Reselected!", Toast.LENGTH_SHORT).show();
}
}
@SuppressLint("ValidFragment")
private class TabContentFragment extends Fragment {
private String mText;
public TabContentFragment(String text) {
mText = text;
}
public String getText() {
return mText;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View fragView = inflater.inflate(R.layout.activity_main, container, false);
TextView text = (TextView) fragView.findViewById(R.id.text);
text.setText(mText);
return fragView;
}
}
public void ChangeFont(View view) {
Button b = (Button) findViewById(R.id.Font);
PopupMenu popupMenu = new PopupMenu(MainActivity.this, b);
popupMenu.getMenuInflater().inflate(R.menu.popupmenu,
popupMenu.getMenu());
popupMenu
.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
EditText text = (EditText) findViewById(R.id.TextBox);
@Override
public boolean onMenuItemClick(MenuItem item) {
switch (item.getItemId()) {
case R.id.menu1: {
tf=Typeface.SANS_SERIF;
text.setTypeface(tf,sty);
break;
}
case R.id.menu2: {
tf=Typeface.SERIF;
text.setTypeface(tf,sty);
break;
}
case R.id.menu3: {
tf=Typeface.MONOSPACE;
text.setTypeface(tf,sty);
break;
}
case R.id.menu4: {
tf = Typeface.createFromAsset(getAssets(),
"Fonts/HandmadeTypewriter.ttf");
text.setTypeface(tf,sty);
break;
}
case R.id.menu5: {
tf = Typeface.createFromAsset(getAssets(),
"Fonts/verdana.ttf");
text.setTypeface(tf,sty);
break;
}
case R.id.menu6: {
tf = Typeface.createFromAsset(getAssets(),
"Fonts/times.ttf");
text.setTypeface(tf,sty);
break;
}
case R.id.menu7: {
tf = Typeface.createFromAsset(getAssets(),
"Fonts/babe bamboo.ttf");
text.setTypeface(tf,sty);
break;
}
case R.id.menu8: {
tf = Typeface.createFromAsset(getAssets(),
"Fonts/O_Connor.ttf");
text.setTypeface(tf,sty);
break;
}
case R.id.menu9: {
tf = Typeface.createFromAsset(getAssets(),
"Fonts/OBLIVIOUSFONT.TTF");
text.setTypeface(tf,sty);
break;
}
default: {
break;
}
}
return true;
}
});
popupMenu.show();
}
public void ChangeStyle(View view) {
Button b = (Button) findViewById(R.id.Style);
PopupMenu popupMenu = new PopupMenu(MainActivity.this, b);
popupMenu.getMenuInflater().inflate(R.menu.stylemenu,
popupMenu.getMenu());
popupMenu
.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
EditText text = (EditText) findViewById(R.id.TextBox);
@Override
public boolean onMenuItemClick(MenuItem item) {
switch (item.getItemId()) {
case R.id.type1: {
sty=Typeface.ITALIC;
text.setTypeface(tf, sty);
break;
}
case R.id.type2: {
sty=Typeface.BOLD;
text.setTypeface(tf, sty);
break;
}
case R.id.type3: {
sty=Typeface.BOLD_ITALIC;
text.setTypeface(tf, sty);
break;
}
case R.id.type4: {
sty=Typeface.NORMAL;
text.setTypeface(tf, sty);
break;
}
default: {
break;
}
}
return true;
}
});
popupMenu.show();
}
public void ChangeSize(View view) {
Button b = (Button) findViewById(R.id.Size);
PopupMenu popupMenu = new PopupMenu(MainActivity.this, b);
popupMenu.getMenuInflater().inflate(R.menu.sizemenu,
popupMenu.getMenu());
popupMenu
.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
EditText text = (EditText) findViewById(R.id.TextBox);
@Override
public boolean onMenuItemClick(MenuItem item) {
switch (item.getItemId()) {
case R.id.size1: {
text.setTextSize(14);
break;
}
case R.id.size2: {
text.setTextSize(16);
break;
}
case R.id.size3: {
text.setTextSize(18);
break;
}
case R.id.size4: {
text.setTextSize(20);
break;
}
case R.id.size5: {
text.setTextSize(22);
break;
}
case R.id.size6: {
text.setTextSize(24);
break;
}
case R.id.size7: {
text.setTextSize(26);
break;
}
case R.id.size8: {
text.setTextSize(28);
break;
}
default: {
break;
}
}
return true;
}
});
popupMenu.show();
}
public synchronized void onActivityResult(final int requestCode,
int resultCode, final Intent data) {
EditText text = (EditText) findViewById(R.id.TextBox);
if (resultCode == Activity.RESULT_OK) {
if(requestCode==0){
String filePath = data.getStringExtra(FileDialog.RESULT_PATH);
File file = new File(filePath);
StringBuilder info = new StringBuilder();
try {
BufferedReader br = new BufferedReader(new FileReader(file));
String line;
while ((line = br.readLine()) != null) {
info.append(line);
info.append('\n');
}
text.setText(info);
br.close();
} catch (IOException e) {
// You'll need to add proper error handling here
}
}
else if(requestCode==1){
String filePath = data.getStringExtra(FileDialog.RESULT_PATH);
File file = new File(filePath);
FileOutputStream fos;
byte[] data1 = text.getText().toString().getBytes();
try {
fos = new FileOutputStream(file);
fos.write(data1);
fos.flush();
fos.close();
} catch (FileNotFoundException e) {
// handle exception
} catch (IOException e) {
// handle exception
}
}
} else if (resultCode == Activity.RESULT_CANCELED) {
text.setText("file not selected");
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.options, menu);
return super.onCreateOptionsMenu(menu);
}
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.item1:
Intent intent = new Intent(getBaseContext(), FileDialog.class);
intent.putExtra(FileDialog.START_PATH, "/sdcard");
intent.putExtra(FileDialog.CAN_SELECT_DIR, true);
startActivityForResult(intent, 0);
break;
case R.id.item2:
Intent intent1 = new Intent(getBaseContext(), FileDialog.class);
intent1.putExtra(FileDialog.START_PATH, "/sdcard");
intent1.putExtra(FileDialog.CAN_SELECT_DIR, true);
startActivityForResult(intent1, 1);
break;
case R.id.item3:
Context context = this;
AlertDialog.Builder alertDialog = new AlertDialog.Builder(context);
alertDialog.setTitle("NEW");
alertDialog.setMessage("Do you wish to save the file");
alertDialog.setPositiveButton("OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
Intent intent = new Intent(getBaseContext(),
FileDialog.class);
intent.putExtra(FileDialog.START_PATH, "/sdcard");
intent.putExtra(FileDialog.CAN_SELECT_DIR, true);
startActivityForResult(intent, 1);
EditText text = (EditText) findViewById(R.id.TextBox);
text.setText("");
}
});
alertDialog.setNegativeButton("No",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
EditText text = (EditText) findViewById(R.id.TextBox);
text.setText("");
}
});
alertDialog.show();
Toast.makeText(getApplicationContext(), "New file",
Toast.LENGTH_SHORT).show();
break;
case R.id.item4:
onAddTab();
break;
case R.id.item5:
onRemoveTab();
break;
case R.id.item6:
onToggleTabs();
break;
default:
break;
}
return super.onOptionsItemSelected(item);
}
}
这是logcat：
03-04 18:55:19.229: E/AndroidRuntime(20619): FATAL EXCEPTION: main
03-04 18:55:19.229: E/AndroidRuntime(20619): java.lang.NullPointerException
03-04 18:55:19.229: E/AndroidRuntime(20619): at com.example.notepadxl.MainActivity$TabContentFragment.onCreateView(MainActivity.java:178)
03-04 18:55:19.229: E/AndroidRuntime(20619): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:828)
03-04 18:55:19.229: E/AndroidRuntime(20619): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1032)
03-04 18:55:19.229: E/AndroidRuntime(20619): at android.app.BackStackRecord.run(BackStackRecord.java:622)
03-04 18:55:19.229: E/AndroidRuntime(20619): at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1382)
03-04 18:55:19.229: E/AndroidRuntime(20619): at android.app.FragmentManagerImpl$1.run(FragmentManager.java:426)
03-04 18:55:19.229: E/AndroidRuntime(20619): at android.os.Handler.handleCallback(Handler.java:605)
03-04 18:55:19.229: E/AndroidRuntime(20619): at android.os.Handler.dispatchMessage(Handler.java:92)
03-04 18:55:19.229: E/AndroidRuntime(20619): at android.os.Looper.loop(Looper.java:137)
03-04 18:55:19.229: E/AndroidRuntime(20619): at android.app.ActivityThread.main(ActivityThread.java:4441)
03-04 18:55:19.229: E/AndroidRuntime(20619): at java.lang.reflect.Method.invokeNative(Native Method)
03-04 18:55:19.229: E/AndroidRuntime(20619): at java.lang.reflect.Method.invoke(Method.java:511)
03-04 18:55:19.229: E/AndroidRuntime(20619): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
03-04 18:55:19.229: E/AndroidRuntime(20619): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
03-04 18:55:19.229: E/AndroidRuntime(20619): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
堆栈跟踪说onCreateView()中有一个NPE：
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View fragView = inflater.inflate(R.layout.activity_main, container, false);
TextView text = (TextView) fragView.findViewById(R.id.text);
text.setText(mText);
return fragView;
}
您的activity_main布局似乎不包含ID为text的视图。
答案 1 :(得分：0)
请检查activity_main是否包含ID为text的元素。
显然它不存在。