试过很多方法，但都没有完美的效果。我想从导航视图中设置的片段中获取主要活动。 我试过了
@Override
public void onBackPressed() {
startActivity(new Intent(this, MainActivity.class));
}
但它不能正常运作。我希望它就像当我在一个支离破碎的活动中它返回到main并且再次点击它退出时（我已经这样做了），当我按下后回到主要活动帮助我
MainActivity.java
public class MainActivity extends AppCompatActivity {
private static final int PERMISSION_REQUEST_CODE = 1000 ;
private static final String TAG = "MainActivity";
private AdView mAdView;
ImageView imageView;
RecyclerView recyclerView;
RecyclerView.LayoutManager layoutManager;
List<Item> items;
CustomAdapter adapter;
private long backpressedtime;
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
switch (requestCode)
{
case PERMISSION_REQUEST_CODE:
{
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED)
Toast.makeText(this, "Permission Granted", Toast.LENGTH_SHORT).show();
else
Toast.makeText(this,"Permission Denied", Toast.LENGTH_SHORT).show();
}
break;
}
}
private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle mToggle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
String str="Click on Wallpaper to set Wallpaper";
Toast.makeText(getApplicationContext(), str, Toast.LENGTH_LONG).show();
imageView=(ImageView)findViewById(R.id.imageView);
mDrawerLayout=(DrawerLayout) findViewById(R.id.dl);
mToggle=new ActionBarDrawerToggle(this,mDrawerLayout,R.string.open,R.string.close);
mDrawerLayout.addDrawerListener(mToggle);
mToggle.syncState();
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
NavigationView navigationView = (NavigationView) findViewById(R.id.Navigation_v);
setupDrawerContent(navigationView);
ActionBar actionBar = getSupportActionBar();
recyclerView =(RecyclerView)findViewById(R.id.recyclerView);
recyclerView.setHasFixedSize(true);
layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
imageView=(ImageView)findViewById(R.id.imageView);
initItem();
//start service and play music
startService(new Intent(MainActivity.this, SoundService.class));
}
public void toast(View v) {
Toast.makeText(MainActivity.this, "Wallpaper Set", Toast.LENGTH_LONG).show();
}
private void initItem() {
items = new ArrayList<>();
items.add(new Item(0,"Wide","https://images8.alphacoders.com/532/thumb-1920-532407.jpg"));
items.add(new Item(1, "Wide","https://images5.alphacoders.com/394/thumb-1920-394511.jpg"));
items.add(new Item(1,"Wide","https://images5.alphacoders.com/408/thumb-1920-408539.jpg"));
adapter = new CustomAdapter(this,items);
recyclerView.setAdapter(adapter);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (mToggle.onOptionsItemSelected(item)) {
return true;
}
return super.onOptionsItemSelected(item);
}
protected void onDestroy() {
//stop service and stop music
stopService(new Intent(MainActivity.this, SoundService.class));
super.onDestroy();
}
public void selectItemDrawer(MenuItem menuItem){
Fragment myFragment = null;
Class fragmentClass;
switch (menuItem.getItemId()) {
case R.id.walkthrough:
fragmentClass = Walkthrough.class;
break;
case R.id.info:
fragmentClass = About.class;
break;
default:
fragmentClass = Walkthrough.class;
}
try {
myFragment = (Fragment) fragmentClass.newInstance();
}
catch (Exception e) {
e.printStackTrace();
}
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.flcontent,myFragment).commit();
setTitle(menuItem.getTitle());
mDrawerLayout.closeDrawers();
}
private void setupDrawerContent(NavigationView navigationView) {
navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
selectItemDrawer(item);
return true;
}
});
}
@Override
public void onBackPressed() {
final AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
builder.setMessage("Are you sure you want to exit?");
builder.setCancelable(true);
builder.setNegativeButton("No Stay ;-)", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
dialogInterface.cancel();
}
});
builder.setPositiveButton("Yes :'-(", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
});
AlertDialog alertDialog = builder.create();
alertDialog.show();
}
Walkthrough.java
public class Walkthrough extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public Walkthrough() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment Walkthrough.
*/
// TODO: Rename and change types and number of parameters
public static Walkthrough newInstance(String param1, String param2) {
Walkthrough fragment = new Walkthrough();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View v = inflater.inflate(R.layout.fragment_walkthrough, container, false);
WebView webView = (WebView)v.findViewById(R.id.webView);
webView.getSettings().setJavaScriptEnabled(true); //enable javascript
webView.setWebViewClient(new WebViewClient()); //important to open url in your app
webView.loadUrl("http://ign.com/wikis/the-last-of-us/Prologue");
return v;
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
答案 0 :(得分：3)
如果您想返回 MainActivity onBack点击 WalkthroughFragment ，那么在提交您的片段时，请使用以下方法将其添加到 BackStack ：
FragmentTransaction addToBackStack (String name)
此方法将执行以下操作：
将此事务添加到后台堆栈。这意味着事务将在提交后被记住，并在稍后从堆栈中弹出时将反转其操作。
你可以像那样使用它
FragmentTransaction ftx = getFragmentManager().beginTransaction();
ftx.replace(R.id.my_container_frame, fragment);
ftx.addToBackStack(null);
ftx.commit();
答案 1 :(得分：0)
或者，您将所有函数调用都包含在一行中
getSupportFragmentManager().beginTransaction().replace('Your Fragment Container ID', new 'Fragment Class Name').addToBackStack(null).commit();
干杯！