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我的應用程序中有幾個不同的片段。在我的HelpFragment我有一個Button。我想要做的是，當用戶按Button，然後我希望他們導航到ContactFragment而不是。如何從片段導航到片段按鈕單擊
這是我試過的代碼。這裏的代碼會讓我的應用程序崩潰，因此很顯然這裏有些問題。此代碼位於我MainActivity.java
Button GoToContact=(Button)findViewById(R.id.btnGoToContact);
GoToContact.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
HelpFragment HelpFragment = new HelpFragment();
FragmentManager manager1 = getSupportFragmentManager();
manager1.beginTransaction().replace(R.id.relativelayout_for_fragment,
HelpFragment,
HelpFragment.getTag()
).commit();
}
});
所以，我對於每一個Fragment佈局。所以我的fragment_help佈局是按鈕所在的位置。所以我想他們fragment_help在從fragment_help.xml（佈局）移動到fragment_contact
我的代碼
<Button
android:text="Go to contact"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/btnGoToContact"
style="@android:style/Widget.Button"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true"
android:onClick="GoToContact"/>
這是我在HelpFragment
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class HelpFragment extends Fragment {
public HelpFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_help, container, false);
}
此代碼是怎麼也我的ContactFragment看起來像。這是我創建Fragment時自動生成的代碼。
這是我加載應用程序時出現的錯誤！
--------- beginning of crash
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.sveinung.clock, PID: 2304
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sveinung.clock/com.sveinung.clock.MainActivity}: java.lang.NullPointerException:
Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void
android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.sveinung.clock.MainActivity.onCreate(MainActivity.java:50)
at android.app.Activity.performCreate(Activity.java:6662)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2599)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
這是我的整個MainActivity.java
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View rootView = inflater.inflate(R.layout.fragment_help, container, false);
final Button goToContact = (Button) rootView.findViewById(R.id.btnGoToContact);
goToContact.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
HelpFragment HelpFragment = new HelpFragment();
FragmentManager manager1 = getSupportFragmentManager();
manager1.beginTransaction().replace(R.id.relativelayout_for_fragment,
HelpFragment,
HelpFragment.getTag()
).commit();
}
});
return rootView;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
ClockFragment clockFragment = new ClockFragment();
FragmentManager manager = getSupportFragmentManager();
manager.beginTransaction().replace(R.id.relativelayout_for_fragment,
clockFragment,
clockFragment.getTag()
).commit();
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_clock) {
ClockFragment clockFragment = new ClockFragment();
FragmentManager manager = getSupportFragmentManager();
manager.beginTransaction()
.setCustomAnimations(R.anim.anim_slide_in_from_left, R.anim.anim_slide_out_from_left)
.replace(R.id.relativelayout_for_fragment,
clockFragment,
clockFragment.getTag()
).commit();
} else if (id == R.id.nav_world_clock) {
Toast.makeText(this, "Coming soon ", Toast.LENGTH_SHORT).show();
/*WorldClockFragment worldClockFragment = new WorldClockFragment();
FragmentManager manager = getSupportFragmentManager();
manager.beginTransaction()
.setCustomAnimations(R.anim.anim_slide_in_from_left, R.anim.anim_slide_out_from_left)
.replace(R.id.relativelayout_for_fragment,
worldClockFragment,
worldClockFragment.getTag()
).commit();*/
} else if (id == R.id.nav_timer) {
Toast.makeText(this, "Coming soon ", Toast.LENGTH_SHORT).show();
} else if (id == R.id.nav_stopwatch) {
Toast.makeText(this, "Coming soon ", Toast.LENGTH_SHORT).show();
} else if (id == R.id.nav_alarm) {
Toast.makeText(this, "Coming soon ", Toast.LENGTH_SHORT).show();
} else if (id == R.id.nav_help) {
//Toast.makeText(this, "Coming soon ", Toast.LENGTH_SHORT).show();
HelpFragment HelpFragment = new HelpFragment();
FragmentManager manager = getSupportFragmentManager();
manager.beginTransaction()
.setCustomAnimations(R.anim.anim_slide_in_from_left, R.anim.anim_slide_out_from_left)
.replace(R.id.relativelayout_for_fragment,
HelpFragment,
HelpFragment.getTag()
).commit();
} else if (id == R.id.nav_contact) {
//Toast.makeText(this, "Coming soon ", Toast.LENGTH_SHORT).show();
ContactFragment contactFragment = new ContactFragment();
FragmentManager manager = getSupportFragmentManager();
manager.beginTransaction()
.setCustomAnimations(R.anim.anim_slide_in_from_left, R.anim.anim_slide_out_from_left)
.replace(R.id.relativelayout_for_fragment,
contactFragment,
contactFragment.getTag()
).commit();
} else if (id == R.id.nav_about) {
Toast.makeText(this, "Coming soon ", Toast.LENGTH_SHORT).show();
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
你可以添加stacktrace到你的問題嗎？ – PPartisan