java - 安卓 : bundle passing

Question

我必须将一个值从我的第一个 Activity 传递到第四个 Activity ...add2cart.java 是我的第三个 Activity ，buy_ltr.java 是我的第四个 Activity 。我想在第三个 Activity 中单击按钮时传递 bundle ，它应该进入第四个 Activity ，必须在其编辑文本字段中设置值。但是它不能正常工作。请帮助我。

每次模拟器因空点异常而崩溃时，我都会在add2cart.java中进行尝试

sme=bundl.getString("dtls");

我的尝试及其结果

1.传递值并在编辑文本中设置。但单击 add2cart 按钮时崩溃

  Intent in=getIntent();

  Bundle bundl=in.getExtras();

  sme=bundl.getString("dtls");

2. Intent 点击add2cart按钮进入下一页。但编辑文本字段为空。

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

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

3.传递值并在编辑文本中设置。但单击 add2cart 按钮时崩溃

 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();

        }
    });
}

}

日志猫

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

从您发送的地方

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

到您收货的地方

 @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
 }        
 }