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我試圖創建和使用動態選項卡，但如果使用切換，添加或刪除選項卡一次應用程序工作正常，但只要我嘗試選擇第二個操作應用程序崩潰。我知道問題出在標籤代碼，因爲該應用程序是標籤部分應用程序在使用動態選項卡時第二次崩潰
這是我MainActivity.java前工作的罰款：
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);
}
}
這是logcat的：
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)