Question

我试图在按下按钮时将activity1中的EditText框中的数字传递给activity2，然后我希望在activity2中按下操作栏按钮时，该数字出现在toast或对话框中。我已经设置了一个意图并编码了我认为应该工作的内容，但它似乎每次都会崩溃activity2。我输入了应该获取变量的代码行。希望有人能够看到它在哪里我出错了。我知道在变量中传递数据应该是一项相当容易的任务。
任何帮助将不胜感激。

Activity1:

public class activity1 extends Activity {


@Override
protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);
//this.requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.screen_settings);
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

final EditText inputTxt1 = (EditText) findViewById(R.id.conPhoneNum);    
Button saveBtn1 = (Button) findViewById(R.id.btnSave1);


  saveBtn1.setOnClickListener(new View.OnClickListener() {
       @Override
       public void onClick(View view) {
          String phoneNum1 = inputTxt1.getText().toString();
          savenum1(phoneNum1);

  Intent passIntent = new Intent();
  passIntent.putExtra("phoneNum", phoneNum1);

    }
    });
}


public void savenum1(String phoneNum1) {

AlertDialog.Builder dlgAlert  = new AlertDialog.Builder(this);

dlgAlert.setMessage("Saved " + phoneNum1);
dlgAlert.setPositiveButton("OK", null);
dlgAlert.setCancelable(true);

dlgAlert.setPositiveButton("Ok",
    new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int which) {
          //dismiss the dialog  
        }
    });    
dlgAlert.create().show();
}
}

活性2：

public class Activity2 extends Activity {

      //This is the line that stops the activity from running
String conPhoneNum = getIntent().getExtras().getString("phoneNum");


@SuppressLint("CutPasteId")
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//this.requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);

ActionBar actionBar = getActionBar();
actionBar.hide();
actionBar.show();
actionBar.setCustomView(R.layout.actionbar_custom_view_home);
actionBar.setDisplayShowCustomEnabled(true);
actionBar.setDisplayShowHomeEnabled(false);
 }


public boolean onCreateOptionsMenu1(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.main, menu);
    return true;
}





@Override  public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case R.id.menu_load:
     Toast toast= Toast.makeText(this, conPhoneNumber, Toast.LENGTH_SHORT);
      toast.setGravity(Gravity.CENTER, 0, -100);
          toast.show();
      break;

         default:
             break;
             }
    return true;
    } 
 }

LogCat信息：

07-31 15:51:50.135: E/AndroidRuntime(779): FATAL EXCEPTION: main
07-31 15:51:50.135: E/AndroidRuntime(779): java.lang.RuntimeException: Unable to start activity     ComponentInfo{com.cam.data /com.cam.data.Activity2}: java.lang.NullPointerException
 07-31 15:51:50.135: E/AndroidRuntime(779):     at     android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110)
 07-31 15:51:50.135: E/AndroidRuntime(779):     at     android.app.ActivityThread.handleLaunchActivity     (ActivityThread.java:2135)
 07-31 15:51:50.135: E/AndroidRuntime(779):     at android.app.ActivityThread.access$700    (ActivityThread.java:140)
 07-31 15:51:50.135: E/AndroidRuntime(779):     at android.app.ActivityThread$H.handleMessage     (ActivityThread.java:1237)
 07-31 15:51:50.135: E/AndroidRuntime(779):     at android.os.Handler.dispatchMessage     (Handler.java:99)
07-31 15:51:50.135: E/AndroidRuntime(779):  at android.os.Looper.loop(Looper.java:137)
 07-31 15:51:50.135: E/AndroidRuntime(779):     at android.app.ActivityThread.main    (ActivityThread.java:4921)
 07-31 15:51:50.135: E/AndroidRuntime(779):     at java.lang.reflect.Method.invokeNative(Native Method)
07-31 15:51:50.135: E/AndroidRuntime(779):  at java.lang.reflect.Method.invoke(Method.java:511)
 07-31 15:51:50.135: E/AndroidRuntime(779):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1027)
07-31 15:51:50.135: E/AndroidRuntime(779):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794)
07-31 15:51:50.135: E/AndroidRuntime(779):  at dalvik.system.NativeStart.main(Native Method)
07-31 15:51:50.135: E/AndroidRuntime(779): Caused by: java.lang.NullPointerException
07-31 15:51:50.135: E/AndroidRuntime(779):  at com.cam.data.Activity2.onCreate(Activity2.java:66)
 07-31 15:51:50.135: E/AndroidRuntime(779):     at android.app.Activity.performCreate(Activity.java:5206)
07-31 15:51:50.135: E/AndroidRuntime(779):  at     android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
07-31 15:51:50.135: E/AndroidRuntime(779):  at      android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)

更新1： conPhoneNum = getIntent().getExtras().getString("phoneNum");仍在崩溃活动。我发现如果我删除.getExtras()然后它不会崩溃但它也不会显示数据。我不知道这是否是为什么它让应用程序崩溃的原因？也许有人可以提供帮助

更新2：
只是对此的更新，我最终废弃了这个并且只使用全局类中定义的全局变量，任何时候都可以被任何活动使用。除非你绝对需要传递变量，否则它似乎是一种更好的方法来做这种事情显然，如果有人能够弄清楚为什么它不起作用会很好，这会让其他人遇到这个问题

Answer 1

替换此

  Intent passIntent = new Intent();
  passIntent.putExtra("phoneNum", phoneNum1);

通过

  Intent passIntent = new Intent(Activity1.this,Activity2.class);
  passIntent.putExtra("phoneNum", phoneNum1);
  startActivity(passIntent);

进入Activity2：

将conPhoneNum声明为类成员

  String conPhoneNum ;

在onCreate

  conPhnoneNum = getIntent().getExtras().getString("phoneNum");

然后

  Toast toast= Toast.makeText(this, conPhoneNumber, Toast.LENGTH_SHORT);

Answer 2

移动此

String conPhoneNum = getIntent().getExtras().getString("phoneNum");

到onCreate()或至少是初始化

String conPhoneNum; 


@SuppressLint("CutPasteId")
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//this.requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);

conPhoneNum = getIntent().getExtras().getString("phoneNum");  // here

ActionBar actionBar = getActionBa

getIntent()会在null创建之前返回Activity，因此您不得在之前调用它。

Answer 3

在您的第一个活动中：

Intent passIntent = new Intent();
passIntent.putExtra("phoneNum", phoneNum1);
startActivity(intent)

在第二项活动中：

super.onCreate(savedInstanceState);
//this.requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
String conPhoneNum = getIntent().getExtras().getString("phoneNum");

在活动之间传递变量值

3 个答案: