Java 带if条件的按钮

我是Android新手，我正试图用一个按钮打开2个活动，但对我来说不起作用。 例如： 在

mainacivity

上，有

btn_数学

和

btn_物理

打开相同的活动（

Main2acitivity

）并找到

btn_semest1

和

btn_semest2

，每个按钮将为学期模块打开两个其他活动

如果MainActivity上的用户单击：

btn\u数学

-->

btn\u semester1

-->将具有

模块mat

如果单击btn_semester1相同的按钮：

btn\U物理

-->

btn\U semester1

-->将具有

模块HY

main活动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"/>

<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"/>

@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);
    }


}

@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);
    }

}

Main2Activity.java:

<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"/>

<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"/>

@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);
    }


}

@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);
    }

}

---

在MainActivity中，您可以将用于识别的id传递到Main2Activity中。
main活动

   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);
}

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);
    }

}

main2活动

   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);
}

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);
    }

}

---

您可以通过

Intent

在活动之间传递数据。这是一个例子谢谢你的评论，我可以有一个关于我的代码的例子吗？你应该使用

..equals（…）

来比较

字符串

s，而不是

=

你帮了我很多，非常感谢你，我的第二个活动中有一个小问题，你的代码：

如果（id==“Math”）{i=新的意图（this，ModulesMAT2.class）；startActivity（i）；}else如果（id=“Physics”）{i=newintent（this，ModulesPHY2.class）；startActivity（i）；}

i拥有（无法解析符号'i'），只需在每个i之前添加Intent。比如：Intent i=newintent（this，ModulesMAT2.class）；