Android：捆绑传递

Question

I have to pass a value from my first activity to fourth activity...add2cart.java is my third activity and buy_ltr.java is my fourth activity.I want to pass the bundle on button click in third activity and it should be get in fourth activity and have to set the values in its edit text field.But Its not working fine.Please help me.

I made my tries in add2cart.java.In every time the emulator crashes because of Null point exception in line

sme=bundl.getString("dtls");

My Tries and its results

1.Pass values and set in edit text.But crashes on clicking add2cart button

  Intent in=getIntent();

  Bundle bundl=in.getExtras();

  sme=bundl.getString("dtls");

2.Intent to next page clicking add2cart button.But edit text fields are blank.

  if(first_init){   
         sme = "some_value";
          first_init = false;
        }

      else{
         Intent in=getIntent();
         Bundle bundl=in.getExtras();
         sme=bundl.getString("dtls");
        }

3.Pass values and set in edit text.But crashes on clicking add2cart button

 if(first_init){    
         Intent in=getIntent();
         Bundle bundl=in.getExtras();
         sme=bundl.getString("dtls");
               }
  else{
         sme = "some_value";
         first_init = false;

        }

add2cart.java

public class add2cart extends Activity{
ListView adlstvw;
Button btn,remove_btn;
SQLiteDatabase mydb;
@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.add2crt);
    adlstvw=(ListView)findViewById(R.id.lstvw_add2crt);
    btn=(Button)findViewById(R.id.place_order);

     Intent in=getIntent();
     Bundle bundl=in.getExtras();
     sme=bundl.getString("dtls");

    mydb=add2cart.this.openOrCreateDatabase("addcart", MODE_PRIVATE, null);
    Cursor cr = mydb.rawQuery("SELECT * FROM add2cart", null);
    String [] pname = new String[cr.getCount()];
    String [] price = new String[cr.getCount()];

    int i = 0;
    while(cr.moveToNext())
    {
        String name = cr.getString(cr.getColumnIndex("pnme"));
        String prprice = cr.getString(cr.getColumnIndex("prate"));
        pname[i] = name;
        price[i] = prprice;
        i++;
    }
    CartAdapter cart=new CartAdapter(this,pname,price);
    adlstvw.setAdapter(cart);

    btn.setOnClickListener(new OnClickListener() {

         @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            Intent in=new Intent(add2cart.this,buy_ltr.class); 
            Bundle bndl = new Bundle();
            bndl.putString("som",sme); 
            in.putExtras(bndl);
            startActivity(in);

        }
    });

}

}

Buy_ltr.java

public class buy_ltr extends Activity {
EditText edt1,edt2,edt3,edt4,edt5;
Button btn;
SQLiteDatabase mydb;
@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.buy_ltr);
    edt1=(EditText)findViewById(R.id.nameedit);
    edt2=(EditText)findViewById(R.id.addrsedit);
    edt3=(EditText)findViewById(R.id.cityedit);
    edt4=(EditText)findViewById(R.id.pincodedit);
    edt5=(EditText)findViewById(R.id.mobedit);
    btn=(Button)findViewById(R.id.cnfm_ordr);


    Intent in=getIntent();
    Bundle bndl=in.getExtras();
    String cont=bndl.getString("som");

    mydb=this.openOrCreateDatabase("shopping", MODE_PRIVATE, null);
    mydb.execSQL("CREATE TABLE IF NOT EXISTS contacts(name varchar,adrs varchar,city varchar,pin varchar," +
            "uname varchar,pass varchar,mob varchar,eid varchar)");

    Cursor cur=mydb.rawQuery("SELECT * FROM contacts WHERE uname='"+cont+"' ", null);
    while (cur.moveToNext()) {

        String nm=cur.getString(cur.getColumnIndex("name"));
        edt1.setText(nm);
        String ad=cur.getString(cur.getColumnIndex("adrs"));
        edt2.setText(ad);
        String cty=cur.getString(cur.getColumnIndex("city"));
        edt3.setText(cty);
        String pc=cur.getString(cur.getColumnIndex("pin"));
        edt4.setText(pc);   


}
    btn.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

              Intent emailIntent = new Intent(android.content.Intent.ACTION_SEND);
              String[] recipients = new String[]{"my@email.com", "",};
              emailIntent.putExtra(android.content.Intent.EXTRA_EMAIL, recipients);
              emailIntent.putExtra(android.content.Intent.EXTRA_SUBJECT, "Test");
              emailIntent.putExtra(android.content.Intent.EXTRA_TEXT, "This is email's message");
                  emailIntent.putExtra(android.content.Intent.EXTRA_TEXT,"name:"+edt1.getText().toString()+"\n"+"address:"+edt2.getText().toString()+"\n"+"city:"+edt3.getText().toString()+"\n"+"pin:"+edt4.getText().toString());

              emailIntent.setType("message/rfc822");
              startActivity(Intent.createChooser(emailIntent, "Send mail..."));
              finish();

        }
    });
}

}

Log Cat

01-07 23:06:57.093: E/AndroidRuntime(1428): FATAL EXCEPTION: main
01-07 23:06:57.093: E/AndroidRuntime(1428): Process: com.power.it.solar, PID: 1428
01-07 23:06:57.093: E/AndroidRuntime(1428): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.power.it.solar/com.power.it.solar.add2cart}: java.lang.NullPointerException
01-07 23:06:57.093: E/AndroidRuntime(1428):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2176)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at android.app.ActivityThread.access$700(ActivityThread.java:135)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at android.os.Handler.dispatchMessage(Handler.java:102)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at android.os.Looper.loop(Looper.java:137)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at android.app.ActivityThread.main(ActivityThread.java:4998)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at java.lang.reflect.Method.invokeNative(Native Method)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at java.lang.reflect.Method.invoke(Method.java:515)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at dalvik.system.NativeStart.main(Native Method)
01-07 23:06:57.093: E/AndroidRuntime(1428): Caused by: java.lang.NullPointerException
01-07 23:06:57.093: E/AndroidRuntime(1428):     at com.power.it.solar.add2cart.onCreate(add2cart.java:35)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at android.app.Activity.performCreate(Activity.java:5243)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
01-07 23:06:57.093: E/AndroidRuntime(1428):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)

Answer 1

from where you are sending

 Intent intent = new Intent();
 intent.setClass(this, Other_Activity.class);
 intent.putExtra("EXTRA_ID", "SOME DATAS");
 startActivity(intent);

to where you are receiving

 @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Bundle extras = getIntent().getExtras();
if (extras != null) {
 String datas= extras.getString("EXTRA_ID");
 if (datas!= null) {
    // do stuff
 }        
 }

Answer 2

The Bundle will pass to another activity if you are starting the activity using the startActity() or startActivityForResult and putting the Bundle as extra. Check if you are getting the bundle(bundle is not null) before getting data from the bundle.