从对象arraylist获取值并将其显示在另一个活动中

Question

public class User implements Parcelable
{
 private  int Id;
 private  String Name;
 private  String Desg;

 public User() {
     super();
}
@Override
public int describeContents() {
    // TODO Auto-generated method stub
     return 0;
 }

 public void writeToParcel(Parcel dest, int flags) {
    dest.writeString(Name);
    dest.writeInt(Id);
    dest.writeString(Desg);

}
  private User(Parcel in){
        this.Name = in.readString();
        this.Id = in.readInt();
        this.Desg = in.readString();

    }

    public static final Parcelable.Creator<User> CREATOR = new Parcelable.Creator<User>() {

        @Override
        public User createFromParcel(Parcel source) {
            return new User(source);
        }

        @Override
        public User[] newArray(int size) {
            return new User[size];
        }
    };
public int getId() {
    return Id;
}
public void setId(int id) {
    this.Id = id;
}
public String getName() {
    return Name;
}
public void setName(String name) {
    this.Name = name;
}
 public String getDesg() {
    return Desg;
}
public void setDesg(String desg) {
    this.Desg = desg;
}
}


public class SecondActivity extends Activity {

ArrayList<User> userlist = new ArrayList<User>();


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.second_layout);

       Button btn = (Button)findViewById(R.id.add);


        btn.setOnClickListener(new OnClickListener(){

         public void onClick(View v)
         {
             EditText name = (EditText)findViewById(R.id.name);
             EditText desg= (EditText)findViewById(R.id.desg);
             EditText id = (EditText)findViewById(R.id.id);
             User user = new User();
             user.setName(name.getText().toString());
             user.setDesg(desg.getText().toString());
             user.setId(Integer.parseInt(id.getText().toString())); //in case if type is integer



         if(userlist.contains(user))
             {
                 Toast.makeText(getBaseContext(), "Already Added", Toast.LENGTH_SHORT).show();
             }
             else{
                 userlist.add(user);


             }
                 Intent intent = new Intent(SecondActivity.this, MainActivity.class);
                 intent.putExtra("userlist",userlist);
                 startActivity(intent);
                 finish();
         }
     });

}



public class MainActivity extends Activity {
   ListView show;
   ArrayList<User> myList= new ArrayList<User>();      
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main); 
     show = (ListView)findViewById(R.id.list);
     myList=   getIntent().getParcelableExtra("userlist");
     ArrayAdapter<User> adapter = new ArrayAdapter<User>(MainActivity.this, android.R.layout.simple_list_item_multiple_choice, myList);
     show.setAdapter(adapter);

     System.out.println(show);

     show.setOnItemClickListener(new AdapterView.OnItemClickListener() {
         @Override
         public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

         CheckedTextView checkedTextView = ((CheckedTextView)view);
         checkedTextView.setChecked(!checkedTextView.isChecked());
         Toast.makeText(getBaseContext(), "Checked", Toast.LENGTH_SHORT).show();
         }      
     });         
}

public void onClick(View v)
{
Intent intent = new Intent(this, SecondActivity.class);
startActivity(intent);
}

I am storing the user input of different datatype in an arraylist and on button click I want to show that user input (arraylist) in a list view of checkboxes. But this code is not working even it has no error. anyone please tell me may be there is some logical issue here?

Answer 1

You can use intent extras in passing values from one activity to another. Here's an example of sending values to the target activity:

Intent intent = new Intent(OriginActivity.this, TargetActivity.class); intent.putExtra("variableName", variableValue); startActivity(intent)

This sends the data "variableName" with its corresponding value to the target activity. In order to retrieve the sent data, you must first get the instance of the intent in the target activity and then call a type-specific function to return the value. You must also supply a default value in case the function cannot find the specified data or the data does not exist. If for example you want to retrieve an integer , you can do it this way:

int retrievedValue= getIntent().getIntExtra("variableName", defaultValue);

PS: You might want to make it a habit separating your activities, models, etc. in different class files.

Answer 2

Best Way

Put

intent.putParcelableArrayListExtra("userlist" , userlist);

Retrieve

myList= (ArrayList<User>) getIntent().getParcelableArrayListExtra("userlist");

Alternate Way

You have to put individually each item of arraylist in intent extra and then retrieve it accordingly.

Intent intent = new Intent(SecondActivity.this, MainActivity.class);
for (int i = 0; i<userlist.size(); i++)
     intent.putExtra("userlist_"+i , userlist.get(i));
intent.putExtra("userlist_size" , userlist.size());
startActivity(intent);
finish();

Now to retrieve it.

ArrayList<User> myList= new ArrayList<User>();  
int size = getIntent().getIntExtra("userlist_size" , 0);
for(int i=0; i<size ; i++){
   myList.add((User)(getIntent().getParcelableExtra("userlist_"+i)))
}