如何防止通过意图将数据传递给多个活动？

Question

I have an activity A that passes data to activity B through Intent. Now Activity B calls Activity C and Activity C calls Activity D. Now Activity D is calling activity B. Now activity B check for the intent data but the Activity D doesn't pass any data.

Now one way to do this is to pass data through C and D and finally get it in B but i would like to know if there is a better way to handle this ?

i would like to add that the data can be an object with a lot of variables and array.

Edit :- The data is necessary for activity B to work.

Thanks in advance.

Answer 1

Use SharedPreferrence;

For storing values;

SharedPreferences sp=getSharedPreferences("Login", Context.MODE_PRIVATE);
SharedPreferences.Editor Ed=sp.edit();
Ed.putString("id",login_id.getText().toString() );
Ed.putString("password",login_password.getText().toString() );
Ed.commit();

For getting values;

SharedPreferences sharedPreferences = getSharedPreferences("Login", MODE_PRIVATE);
String uName = sharedPreferences.getString("id", "");
String password = sharedPreferences.getString("password", "");

Answer 2

You can Check Your Intent is not null and its has Extras value or not by getting Bundle and another check if Bundle oBject is not null then you check keys are there or not in Bundle Object.

Intent intent = getIntent();
 if(intent!=null)
 {
   Bundle bundle =  intent.getExtras();
   if(bundle!=null)
   {
      if(bundle.containsKey("key"))
      {
      //here you can put your code for Actvity B when comes from Activity  A.
      }
   }
 } 

EDIT 1 Use singleTask launchMode in Activity B in manifest file.

android:launchMode="singleTask" 

Answer 3

You can use gson.jar to store class objects into SharedPreferences.

add GSON dependency in Gradle file:

compile 'com.google.code.gson:gson:2.7'

Creating a shared preference:

SharedPreferences  mPrefs = getPreferences(MODE_PRIVATE);

To save:

  Editor prefsEditor = mPrefs.edit();
Gson gson = new Gson();
String json = gson.toJson(MyObject);
prefsEditor.putString("MyObject", json);
prefsEditor.commit();

To Retrieve:

    Gson gson = new Gson();
String json = mPrefs.getString("MyObject", "");
MyObject obj = gson.fromJson(json, MyObject.class);

Answer 4

If the data you are passing is different, then assign a variable (named activity_name ) with the name of the activity that is calling the intent. In this way, you can check if you are coming to activity B from activity A or D.

Let me try to explain with an example:

ActivityA

String activity_name = "ACTIVITY_A";

Intent intent = new Intent(this, ActivityB.class);
intent.putExtra("calling_activity", activity_name);
intent.putExtra("your_data", your_data); 
startActivity(intent);

ActivityB

Intent intent = getIntent();
String callingActivity = intent.getExtras().getString("calling_activity");

if (callingActivity.matches("ACTIVITY_A")) {
    // Do something
} else if (callingActivity.matches("ACTIVITY_D")) {
    // Do something else
}

and in ActivityD

String activity_name = "ACTIVITY_D";

Intent intent = new Intent(this, ActivityB.class);
intent.putExtra("calling_activity", activity_name);
// No passed data in Actiivty D
startActivity(intent);

This same logic can be employed using SharedPreferences as remarked in other answers and comments.

Answer 5

write below code in your activity B.

String str= getIntent().getStringExtra("key");

if (str == null){
str= "";
}