快速提问。
我正在开发一个有 2 个 Activity 的应用程序。
Activity A 使用带有 3 个选项卡的选项卡导航。每个标签都有一个 fragment ，有几个以宿舍命名的按钮。每个按钮作为宿舍名称的 ID，因此，单击宿舍 A 将启动 Activity B , 并使用 case 语句并找到按钮的 ID 将使用 EXTRA 字符串(宿舍名称)启动 Activity B。
Activity B 也使用标签导航，有 3 个标签。一个列出人员，一个列出事件，一个列出 RA 的办公时间。
我的问题是启动 Activity 并将 Extra 添加到 Activity 中，这将根据 Extra 字符串从数据库中添加信息(即单击 Dorm A 将执行 SQL SELECT WHERE Dorm = 'EXTRA' 或其他内容)。我在这里尝试使用教程:http://wptrafficanalyzer.in/blog/itemclick-handler-for-listfragment-in-android/但我的应用程序一直在崩溃。我在这里和那里使用了其他一些教程，试图了解 Fragments 是如何工作的，我对 Android 还不是很熟悉。无需尝试通过 EXTRA，我可以运行 APP 并显示一些带有填充文本或按钮或其他内容的非常简单的 View 。
我尝试使用这里的一些代码:Where/How to getIntent().getExtras() in an Android Fragment?但我不太明白它是如何工作的，当我使用它时，我得到了相同的结果:崩溃。
这是 LogCat，当我尝试获取 String Intent 时，我可以看到 NullPointerException 引发了错误:05-15 20:31:51.278: E/AndroidRuntime(2274): FATAL EXCEPTION: main
05-15 20:31:51.278: E/AndroidRuntime(2274): Process: ege493.test.hawksnesttabs, PID: 2274
05-15 20:31:51.278: E/AndroidRuntime(2274): java.lang.RuntimeException: Unable to start activity ComponentInfo{ege493.test.hawksnesttabs/ege493.test.hawksnesttabs.DormInfo}: java.lang.NullPointerException
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.app.ActivityThread.access$800(ActivityThread.java:135)
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.os.Handler.dispatchMessage(Handler.java:102)
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.os.Looper.loop(Looper.java:136)
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.app.ActivityThread.main(ActivityThread.java:5017)
05-15 20:31:51.278: E/AndroidRuntime(2274): at java.lang.reflect.Method.invokeNative(Native Method)
05-15 20:31:51.278: E/AndroidRuntime(2274): at java.lang.reflect.Method.invoke(Method.java:515)
05-15 20:31:51.278: E/AndroidRuntime(2274): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
05-15 20:31:51.278: E/AndroidRuntime(2274): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
05-15 20:31:51.278: E/AndroidRuntime(2274): at dalvik.system.NativeStart.main(Native Method)
05-15 20:31:51.278: E/AndroidRuntime(2274): Caused by: java.lang.NullPointerException
05-15 20:31:51.278: E/AndroidRuntime(2274): at ege493.test.hawksnesttabs.Fragment_RA.onCreateView(Fragment_RA.java:33)
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.app.Fragment.performCreateView(Fragment.java:1700)
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:890)
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.app.BackStackRecord.run(BackStackRecord.java:684)
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.app.Activity.performStart(Activity.java:5240)
05-15 20:31:51.278: E/AndroidRuntime(2274): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2168)
05-15 20:31:51.278: E/AndroidRuntime(2274): ... 11 more
Activity A:(一些评论是我稍后会尝试修复的其他一些其他问题)
package ege493.test.hawksnesttabs;
import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.Toast;
public class MainActivity extends Activity {
public final static String EXTRA_DORM = "ege493.Dorm";
ActionBar actionBar;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
actionBar = getActionBar(); // Get reference to ActionBar
// 1. Enable ActionBar navigation tabs
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
actionBar.setDisplayShowTitleEnabled(false);
actionBar.setDisplayShowHomeEnabled(false);
// 2. Add the tabs
Tab hasbrouckTab = actionBar.newTab();
Tab parkerTab = actionBar.newTab();
Tab southTab = actionBar.newTab();
String label1 = getResources().getString(R.string.hasbrouck);
hasbrouckTab.setText(label1).setTabListener(
new TabListener<Fragment_Has>(this, R.id.quadParent,
Fragment_Has.class));
String label2 = getResources().getString(R.string.parker);
parkerTab.setText(label2).setTabListener(
new TabListener<Fragment_Parker>(this, R.id.quadParent,
Fragment_Parker.class));
String label3 = getResources().getString(R.string.south);
southTab.setText(label3).setTabListener(
new TabListener<Fragment_South>(this, R.id.quadParent,
Fragment_South.class));
actionBar.addTab(hasbrouckTab);
actionBar.addTab(parkerTab);
actionBar.addTab(southTab);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.activity_home, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch(item.getItemId()) {
case R.id.action_settings:
Toast.makeText(this, "Acton settings selected", Toast.LENGTH_SHORT).show();
break;
default:
break;
}
return true;
}
public void onClick(View v) {
switch(v.getId()) {
case R.id.buttonBevier:
Intent i = new Intent(this, DormInfo.class);
String dorm = "Bevier";
i.putExtra(EXTRA_DORM, dorm);
startActivity(i);
break;
case R.id.buttonCrispell:
i = new Intent(this, DormInfo.class);
dorm = "Crispell";
i.putExtra(EXTRA_DORM, dorm);
startActivity(i);
break;
case R.id.buttonDeyo:
i = new Intent(this, DormInfo.class);
dorm = "Deyo";
i.putExtra(EXTRA_DORM, dorm);
startActivity(i);
break;
case R.id.buttonDuBois:
i = new Intent(this, DormInfo.class);
dorm = "DuBois";
i.putExtra(EXTRA_DORM, dorm);
startActivity(i);
break;
case R.id.buttonLefevre:
i = new Intent(this, DormInfo.class);
dorm = "DuBois";
i.putExtra(EXTRA_DORM, dorm);
startActivity(i);
break;
case R.id.buttonBouton:
i = new Intent(this, DormInfo.class);
dorm = "Bouton";
i.putExtra(EXTRA_DORM, dorm);
startActivity(i);
break;
case R.id.buttonBliss:
i = new Intent(this, DormInfo.class);
dorm = "Bliss";
i.putExtra(EXTRA_DORM, dorm);
startActivity(i);
break;
case R.id.buttonCapen:
i = new Intent(this, DormInfo.class);
dorm = "Capen";
i.putExtra(EXTRA_DORM, dorm);
startActivity(i);
break;
case R.id.buttonCollango:
i = new Intent(this, DormInfo.class);
dorm = "College/Shango";
i.putExtra(EXTRA_DORM, dorm);
startActivity(i);
break;
case R.id.buttonGage:
i = new Intent(this, DormInfo.class);
dorm = "Gage";
i.putExtra(EXTRA_DORM, dorm);
startActivity(i);
break;
case R.id.buttonScudder:
i = new Intent(this, DormInfo.class);
dorm = "Scudder";
i.putExtra(EXTRA_DORM, dorm);
startActivity(i);
break;
case R.id.buttonEsopus:
i = new Intent(this, DormInfo.class);
dorm = "Esopus";
i.putExtra(EXTRA_DORM, dorm);
startActivity(i);
break;
case R.id.buttonLenape:
i = new Intent(this, DormInfo.class);
dorm = "Lenape";
i.putExtra(EXTRA_DORM, dorm);
startActivity(i);
break;
}
}
}
Activity B
package ege493.test.hawksnesttabs;
import android.app.ActionBar;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.app.ActionBar.Tab;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.Toast;
public class DormInfo extends Activity {
ActionBar actionBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_dorm);
// Set up the action bar.
actionBar = getActionBar(); // Get reference to ActionBar
//Using a different Action Bar, the tabs work well, but...
//I'm trying to get rid of the title/icon/options menu. The Theme.Holo.NoActionBar
//causes it to crash, and I can't get an 'onCreateOptionsMenu' to work.
//Trying to allow a menu to work through hitting the menu button on the phone, but I do not want an
//option for it in the action bar, or an action bar at all (which, I currently have no action bar)
//Goal for this:::: Use the menu button to bring you back to dorm selection if you are already in the app
// 1. Enable ActionBar navigation tabs
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
actionBar.setDisplayShowTitleEnabled(false);
actionBar.setDisplayShowHomeEnabled(false);
// 2. Add the tabs
Tab peopleTab = actionBar.newTab();
Tab eventsTab = actionBar.newTab();
Tab hoursTab = actionBar.newTab();
String label1 = getResources().getString(R.string.ra_list);
peopleTab.setText(label1).setTabListener(
new TabListener<Fragment_RA>(this, R.id.dormParent,
Fragment_RA.class));
String label2 = getResources().getString(R.string.dorm_events);
eventsTab.setText(label2).setTabListener(
new TabListener<Fragment_Events>(this, R.id.dormParent,
Fragment_Events.class));
String label3 = getResources().getString(R.string.dorm_hours);
hoursTab.setText(label3).setTabListener(
new TabListener<Fragment_Hours>(this, R.id.dormParent,
Fragment_Hours.class));
actionBar.addTab(peopleTab);
actionBar.addTab(eventsTab);
actionBar.addTab(hoursTab);
//--------------------------------------------------------
//Get the buttonID from the button that started the activity
//--------------------------------------------------------
/*Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_DORM);
TextView tv = new TextView(this);
tv.setTextSize(40);
tv.setText(message);
setContentView(tv);*/
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransacton = fragmentManager.beginTransaction();
Fragment_RA detailsFragment = new Fragment_RA();
//Fragment_Hours hoursFragment = new Fragment_Hours();
//Fragment_Events eventsFragment = new Fragment_Events();
Bundle b = new Bundle();
b.putString(MainActivity.EXTRA_DORM, getIntent().getStringExtra(MainActivity.EXTRA_DORM));
detailsFragment.setArguments(b);
//fragmentTransacton.add(R.id.dormParent, detailsFragment);
//hoursFragment.setArguments(b);
//fragmentTransacton.add(R.id.dormParent, hoursFragment);
//eventsFragment.setArguments(b);
//fragmentTransacton.add(R.id.dormParent, eventsFragment);
fragmentTransacton.commit();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.activity_home, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch(item.getItemId()) {
case R.id.action_settings:
Toast.makeText(this, "Acton settings selected", Toast.LENGTH_SHORT).show();
break;
default:
break;
}
return true;
}
}
试图获得额外的 fragment
package ege493.test.hawksnesttabs;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class Fragment_RA extends Fragment{
/* public static Fragment_RA newInstance(int index) {
Fragment_RA f = new Fragment_RA();
// Supply index input as an argument.
Bundle args = new Bundle();
args.putInt("index", index);
f.setArguments(args);
return f;
}
public int getShownIndex() {
return getArguments().getInt("index", 0);
}
*/
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.people_fragment, null);
TextView tv = (TextView) v.findViewById(R.id.tv);
Bundle b = getArguments();
tv.setText("Details of " + b.getString(MainActivity.EXTRA_DORM));
return v;
}
}
编辑，我成功了
我弄清楚发生了什么。
我正在使用一种自定义 TabListener 类。我用这个:
how to initialize(pass arguments) fragments for action bar tabs?
它就像一个魅力，所以现在我的 Activity B 的代码，我只是添加了一个 peopleTab.setTag(b);在我将它们添加到操作栏之前，然后在我的 TabListener 类中添加
fragment = Fragment.instantiate(activity, fragmentClass.getName(), (Bundle) tab.getTag());
就像上面的链接解释的那样。我想我只是看得太远了!我倾向于用蚁丘造山……不过还是谢谢你的支持!
最佳答案
您还需要在 Activity 上 bundle 字符串。
Passing a bundle on startActivity
您是否检查过是否也有一个值被传递？您是否运行调试器以查看是否正在传递值？
关于java - 选项卡式导航，将 Intent 附加信息传递给 fragment ，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/23691077/