Android：啓動Activity從onCreate失敗，但從onActivityResult工作

Question

我有一個ProductActivity.class，我想從各種活動啓動。我可以從以下的ReaderActivity類中成功地從onActivityResult啓動它，但無法從其他類的onCreate方法啓動它。我錯過了什麼？

public class ReaderActivity extends AppCompatActivity { 

private Button scan_btn, verifyButton; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_reader); 
     scan_btn = (Button) findViewById(R.id.scan_btn); 
     verifyButton = (Button) findViewById(R.id.buttonVerify); 
     final Activity activity = this; 



     scan_btn.setOnClickListener(new View.OnClickListener() { 
       @Override 
       public void onClick(View view) { 
        ((myApplication) activity.getApplication()).setWhichButton("scan"); 
        IntentIntegrator integrator = new IntentIntegrator(activity); 
        integrator.setDesiredBarcodeFormats(IntentIntegrator.ALL_CODE_TYPES); 
        integrator.setCameraId(0); 
        integrator.initiateScan(); 


       } 
      }); 

     verifyButton.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       ((myApplication) activity.getApplication()).setWhichButton("verify"); 
       IntentIntegrator integrator = new IntentIntegrator(activity); 
       integrator.setDesiredBarcodeFormats(IntentIntegrator.ALL_CODE_TYPES); 
       integrator.setCameraId(0); 
       integrator.initiateScan(); 

      } 
     }); 
    } 


protected void onActivityResult(int requestCode, int resultCode, Intent data) { 

     IntentResult result = IntentIntegrator.parseActivityResult(requestCode, resultCode, data); 

     String val = ((myApplication) this.getApplication()).getWhichButton(); 

if (result !=null) { 
//....more code... 

if (condition1) { 
Intent intentVerifyFail = new Intent(getBaseContext(), VerifyFailActivity.class); 
           startActivity(intentVerifyFail); 
} 
if (condition2){ 

Intent intentVerifySuccess = new Intent(getBaseContext(), VerifySuccessActivity.class); 
            intentVerifySuccess.putExtra("ID", results); 
            startActivity(intentVerifySuccess); 
} 

} 

if(condition3){ 

Intent intentProduct = new Intent(getBaseContext(), ProductActivity.class); 
          intentProduct.putExtra("ID", finalResults); 
          intentProduct.putExtra("SIGNER", accountOut); 
          intentProduct.putExtra("TIME", sTime); 
          startActivity(intentProduct); 
} 
} 
} 

無論從VerifiySuccessActivity和VerifyFailActivity

現在，如果我嘗試推出ProductActivity.class，它崩潰以下

public class VerifySuccessActivity extends AppCompatActivity { 

    private Button OKButton; 
    private EditText productIDVerified; 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_verify_success); 
     OKButton = (Button) findViewById(R.id.buttonOKVerifySuccess); 
     productIDVerified = (EditText) findViewById(R.id.textSKUVerified); 

     String productSKU= getIntent().getExtras().getString("ID"); 
     productIDVerified.setText(productSKU, TextView.BufferType.EDITABLE); 

     OKButton.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 

       Intent intent = new Intent(getBaseContext(), ProductActivity.class); 

       startActivity(intent); 

      } 
     }); 
    } 
} 

錯誤代碼：

FATAL EXCEPTION: main 
                       Process: com.example.newpc.qrcode, PID: 24682 
                       java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.newpc.qrcode/com.example.newpc.qrcode.ProductActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference 
                        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2521) 
                        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2595) 
                        at android.app.ActivityThread.access$800(ActivityThread.java:178) 
                        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1470) 
                        at android.os.Handler.dispatchMessage(Handler.java:111) 
                        at android.os.Looper.loop(Looper.java:194) 
                        at android.app.ActivityThread.main(ActivityThread.java:5631) 
                        at java.lang.reflect.Method.invoke(Native Method) 
                        at java.lang.reflect.Method.invoke(Method.java:372) 
                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:959) 
                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754) 
                       Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference 
                        at com.example.newpc.qrcode.ProductActivity.onCreate(ProductActivity.java:21) 
                        at android.app.Activity.performCreate(Activity.java:6092) 
                        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1112) 
                        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2468) 
                        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2595)  
                        at android.app.ActivityThread.access$800(ActivityThread.java:178)  
                        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1470)  
                        at android.os.Handler.dispatchMessage(Handler.java:111)  
                        at android.os.Looper.loop(Looper.java:194)  
                        at android.app.ActivityThread.main(ActivityThread.java:5631)  
                        at java.lang.reflect.Method.invoke(Native Method)  
                        at java.lang.reflect.Method.invoke(Method.java:372)  
                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:959)  
                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754)  

Answer 1

此行導致崩潰

​​3210

你應該檢查你得到的附加項是否爲空

String productSKU= getIntent().getExtras().getString("ID"); 
Bundle extras = getIntent().getExtras(); 
if (extras != null) { 
    productSku = extras.getString("ID"); 
}