按钮，如果条件

Question

我是新来的Android，我试图做一个按钮打开2个活动，但没有为我工作。 为前： 上Mainacitivity，有btn_mathematics和btn_physics打开相同的活性（Main2acitivity），并找到btn_semester1和btn_semester2，每个按钮将打开其他2个活动学期模块。

如果Mainacitivity用户点击上： btn_mathematics --->btn_semester1 --->将有ModulesMAT 如果放在btn_semester1同一按钮点击： btn_physics --->btn_semester1 --->将有ModulesPHY 。

MainActivity XML：

<Button 
    android:id="@+id/btn_mathematics" 
    android:onClick="btn_mathematics" 
    android:text="@string/btn_mathematics/> 

<Button 
    android:id="@+id/btn_physics" 
    android:onClick="btn_physics" 
    android:text="@string/btn_physics"/> 

Main2Activity XML：

<Button 
    android:id="@+id/btn_semester1" 
    android:onClick="btn_semester1" 
    android:text="@string/btn_semester1"/> 

<Button 
    android:id="@+id/btn_semester2" 
    android:onClick="btn_s2" 
    android:text="@string/btn_semester2"/> 

我想，没有必要添加XML为ModulesMAT和ModulesPHY，它很类似于其他人。

现在的Java代码：

MainActivity.java：

@Override 
protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
    } 

    public void btn_mathematics (View v) { 
     Intent intent = new Intent(MainActivity.this, Main2Activity.class); 
     startActivity(intent); 
    } 

    `public void btn_physics (View v) { 
     Intent intent = new Intent(MainActivity.this, Main2Activity.class); 
     startActivity(intent); 
    } 


} 

Main2Activity.java：

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main2); 
} 



public void btn_semester1 (View v) 
{ 
    Intent i = getIntent(); 
    String id = i.getStringExtra("id"); 
    if(id == "btn_mathematics") 
    { 
     i = new Intent(this, ModulesMAT.class); 
     startActivity(i); 
    } 
    else if (id == "btn_physics") 
    { 
     i = new Intent(this, ModulesPHY.class); 
     startActivity(i); 
    } 

} 


public void btn_semester2 (View v) 
{ 
    Intent i = getIntent(); 
    String id = i.getStringExtra("id"); 
    if(id == "btn_mathematics") 
    { 
     i = new Intent(this, ModulesMAT2.class); 
     startActivity(i); 
    } 
    else if (id == "btn_physics") 
    { 
     i = new Intent(this, ModulesPHY2.class); 
     startActivity(i); 
    } 

} 

Answer 1

在MainActivity你可以通过ID识别成Main2Activity。
MainActivity

public void btn_mathematics (View v) { 
     Intent intent = new Intent(MainActivity.this, Main2Activity.class); 
     Bundle bundle = new Bundle(); 
     bundle.putString("id","Math"); 
     intent.putExtra(bundle); 
     startActivity(intent); 
    } 

public void btn_physics (View v) { 
    Intent intent = new Intent(MainActivity.this, Main2Activity.class); 
    Bundle bundle = new Bundle(); 
    bundle.putString("id","Physics"); 
    intent.putExtra(bundle); 
    startActivity(intent); 
} 

Main2Activity

String id; 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main2); 

    Bundle bundle = getIntent().getExtras(); 
    id= bundle.getString("id"); 
} 

public void btn_semester1 (View v) 
{ 
    if(id == "Math") 
    { 
     i = new Intent(this, ModulesMAT2.class); 
     startActivity(i); 
    } 
    else if (id == "Physics") 
    { 
     i = new Intent(this, ModulesPHY2.class); 
     startActivity(i); 
    } 

} 


public void btn_semester2 (View v) 
{ 
    if(id == "Math") 
    { 
     i = new Intent(this, ModulesMAT2.class); 
     startActivity(i); 
    } 
    else if (id == "Physics") 
    { 
     i = new Intent(this, ModulesPHY2.class); 
     startActivity(i); 
    } 

}