主要活动的错误消息

Question

我是Android Studio的初学者。我正在使用Windows。我的主要活动出现错误。错误：在android中表达式的非法启动。请帮我解决这个问题。提前感谢。

守则是

public class MainActivity extends AppCompatActivity { 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     Button Expense=(Button)findViewById(R.id.Expense); 
     Button Income=(Button) findViewById(R.id.Income); 

     Expense.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View v) { 
       Intent intent = new Intent(MainActivity.this, Addpanel.class); 
       startActivity(intent); 

      } 

     }); 

     Income.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View v) { 

       Intent intent1 = new Intent(MainActivity.this, Addincome.class); 
       startActivity(intent1); 

      } 

     }); 

     public class MainActivity extends ActionBarActivity { 
      DatabaseHelper myDb; 
      EditText editproduct,editamount; 
      Button btnsave; 
      @Override 
      protected void onCreate(Bundle savedInstanceState) { 
       super.onCreate(savedInstanceState); 
       setContentView(R.layout.activity_addpanel); 
       myDb = new DatabaseHelper(this); 
       editproduct = (EditText)findViewById(R.id.product); 
       editamount = (EditText)findViewById(R.id.amount); 
       btnsave = (Button)findViewById(R.id.save); 
       save(); 
      } 
      public void save() { 
       btnsave.setOnClickListener(
         new View.OnClickListener() { 
          @Override 
          public void onClick(View v) { 
           boolean isInserted = myDb.insertData(editproduct.getText().toString(), 
             editamount.getText().toString() 
           ); 
           if(isInserted == true) 
            Toast.makeText(MainActivity.this,"Data Inserted",Toast.LENGTH_LONG).show(); 
           else 
            Toast.makeText(MainActivity.this,"Data not  Inserted",Toast.LENGTH_LONG).show(); 
          } 
         } 
       ); 
      } 
      public void showMessage(String title,String Message){ 
       AlertDialog.Builder builder = new AlertDialog.Builder(this); 
       builder.setCancelable(true); 
       builder.setTitle(title); 
       builder.setMessage(Message); 
       builder.show(); 
      } 
      @Override 
      public boolean onCreateOptionsMenu(Menu menu) { 
       getMenuInflater().inflate(R.menu.menu_main, menu); 
       return true; 
      } 
      @Override 
      public boolean onOptionsItemSelected(MenuItem item) { 
       int id = item.getItemId(); 

       if (id == R.id.action_settings) { 
        return true; 
       } 

       return super.onOptionsItemSelected(item); 
      } 
     } 
    } 
} 

Answer 1

创建了两个MainActivity在你的代码，所以你得到表达的非法启动的错误。你必须在单独的Mainactivity中编写你的代码。

Answer 2

您有两个MainActivity，可能会导致错误。尝试摆脱其中的一个。

Answer 3

在一个类中有两个活动需要为MainActivity创建两个分离的类。