Send data from one activity to a fragment on a sec

问题:

I have a main activity with a navigation drawer and several fragments and a secondary activity that collects some data that I store on a string called "endpoints". I'm trying to send the string from the secondary activity to one of the fragments on the main activity:

Secondary Activity (sending "endpoint" string via intent to the Main activity):

        Intent intent = new Intent(Secondary.this,Main.class);
        intent.putExtra("endpoint",endpoint);
        startActivity(intent);

Main Activity (getting string from the Secondary activity):

    public void onNavigationDrawerItemSelected(int position) {
    // update the main content by replacing fragments
    FragmentManager fragmentManager = getFragmentManager();
    fragmentManager.beginTransaction()
            .replace(R.id.container, PlaceholderFragment.newInstance(position))
            .commit();
    switch (position) {
        case 0:
            Bundle args = new Bundle();
            args.putString("endpoint",getIntent().getExtras().getString("endpoint"));
            Fragment1 fragment = new Fragment1();
            fragment1.setArguments(args);
            fragmentManager.beginTransaction().replace(R.id.container, Fragment1.newInstance(position)).commit();
            break;
        case 1:
            fragmentManager.beginTransaction().replace(R.id.container, Fragment2newInstance(position)).commit();
            break;
        case 2:
            fragmentManager.beginTransaction().replace(R.id.container, Fragment3.newInstance(position)).commit();
            break;
        case 3: ...

And on the Fragment class I'm trying to display the data on a TextView:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    String endpoints = getActivity().getIntent().getStringExtra("endpointStr");
    View rootView = inflater.inflate(R.layout.fragment_overview, container, false);
    TextView textView = (TextView) rootView.findViewById(R.id.overviewTV);
    textView.setText(endpoint);
    return rootView;
}

This is what I get:

E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.Main.app, PID: 16681 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.Main.app/com.Main.app.Main}: android.view.InflateException: Binary XML file line #30: Error inflating class fragment Caused by: android.view.InflateException: Binary XML file line #30: Error inflating class fragment at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:713) at android.view.LayoutInflater.rInflate(LayoutInflater.java:755) at android.view.LayoutInflater.rInflate(LayoutInflater.java:758) at android.view.LayoutInflater.inflate(LayoutInflater.java:492) at android.view.LayoutInflater.inflate(LayoutInflater.java:397) at android.view.LayoutInflater.inflate(LayoutInflater.java:353) at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:343) at android.app.Activity.setContentView(Activity.java:1929) at com.Main.app.Main.onCreate(Main.java:42) at android.app.Activity.performCreate(Activity.java:5231) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169)             at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)             at android.app.ActivityThread.access$800(ActivityThread.java:144)             at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)             at android.os.Handler.dispatchMessage(Handler.java:102)             at android.os.Looper.loop(Looper.java:136)             at android.app.ActivityThread.main(ActivityThread.java:5146)             at java.lang.reflect.Method.invokeNative(Native Method)             at java.lang.reflect.Method.invoke(Method.java:515)             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)             at dalvik.system.NativeStart.main(Native Method)

        **Caused by: java.lang.NullPointerException**
        at com.Main.app.Main.onNavigationDrawerItemSelected(Main.java:65)
        at com.Main.app.NavigationDrawerFragment.selectItem(NavigationDrawerFragment.java:205)
        at com.Main.app.NavigationDrawerFragment.onCreate(NavigationDrawerFragment.java:79)
        at android.app.Fragment.performCreate(Fragment.java:1678)
        at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:859)
        at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1040)
        at android.app.FragmentManagerImpl.addFragment(FragmentManager.java:1142)
        at android.app.Activity.onCreateView(Activity.java:4786)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:689)

            at android.view.LayoutInflater.rInflate(LayoutInflater.java:755)             at android.view.LayoutInflater.rInflate(LayoutInflater.java:758)             at android.view.LayoutInflater.inflate(LayoutInflater.java:492)             at android.view.LayoutInflater.inflate(LayoutInflater.java:397)             at android.view.LayoutInflater.inflate(LayoutInflater.java:353)             at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:343)             at android.app.Activity.setContentView(Activity.java:1929)             at com.Main.app.Main.onCreate(Main.java:42)             at android.app.Activity.performCreate(Activity.java:5231)             at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)             at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169)             at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)             at android.app.ActivityThread.access$800(ActivityThread.java:144)             at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)             at android.os.Handler.dispatchMessage(Handler.java:102)             at android.os.Looper.loop(Looper.java:136)             at android.app.ActivityThread.main(ActivityThread.java:5146)             at java.lang.reflect.Method.invokeNative(Native Method)             at java.lang.reflect.Method.invoke(Method.java:515)             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)             at dalvik.system.NativeStart.main(Native Method)

How can I get it fixed and send the string from one activity to a fragment on another activity?

Here's the XML:

<!-- A DrawerLayout is intended to be used as the top-level content view using match_parent for both width and height to consume the full space available. -->
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true">
    <android.support.v4.widget.DrawerLayout
        android:id="@+id/drawer_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#ffffff"
        tools:context=".Stackerz">

        <!-- As the main content view, the view below consumes the entire
             space available using match_parent in both dimensions. -->
        <FrameLayout
            android:id="@+id/container"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            />

        <!-- android:layout_gravity="start" tells DrawerLayout to treat
             this as a sliding drawer on the left side for left-to-right
             languages and on the right side for right-to-left languages.
             If you're not building against API 17 or higher, use
             android:layout_gravity="left" instead. -->
        <!-- The drawer is given a fixed width in dp and extends the full height of
             the container. -->
        <fragment android:id="@+id/navigation_drawer"
            android:layout_width="@dimen/navigation_drawer_width"
            android:layout_height="match_parent"
            android:layout_gravity="start"
            android:name="com.xxxxxx.app.NavigationDrawerFragment"
            tools:layout="@layout/fragment_navigation_drawer" />

    </android.support.v4.widget.DrawerLayout>
</FrameLayout>

回答1:

Ok, this is how your Constants class should look like.

public class Constants {

public static Constants constants=null;

public static Constants shared(){
    if (constants==null){
        constants = new Constants();
    }
    return constants;
}

public static String endpoint;

public static String getEndpoint() {
    return endpoint;
}

public static void setEndpoint(String endpoint) {
    Constants.endpoint = endpoint;
}

}

Now, in the second activity, do this:

    Constants.shared().setEndpoint(endpoint);
    Intent intent = new Intent(Secondary.this,Main.class);
    startActivity(intent);

And in your Fragment class, do this:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                     Bundle savedInstanceState) {
String endpoint = Constants.shared().getEndpoint;
View rootView = inflater.inflate(R.layout.fragment_overview, container, false);
TextView textView = (TextView) rootView.findViewById(R.id.overviewTV);
textView.setText(endpoint);
return rootView;
}

回答2:

If your Main activity is the central point that delegates data and work to fragments I would also store the information there. If you have a member variable in your Main activity to store your endpoint than each of the fragments can access it via:

((Main) getActivity()).setEndpoint(endpoint)

((Main) getActivity()).getEndpoint()

This way your Main activity is the controller.

回答3:

You don't even have to use intent.putExtra to complete this. You can simply introduce some static variables in your project.

Make a class called Constants.

in that class, make a variable

public static String endpoint;

Then, in your Secondary activity, instead of putExtra, simply do this:

Constants.endpoint = "your value";

Then, in your fragment simply do this:

TextView textView = (TextView) rootView.findViewById(R.id.overviewTV);
textView.setText(Constants.endpoint);