Java Android：返回第一个布局后按钮不起作用

Question

when I press two buttons the picture changes but when I move with the 3 button to the 2nd layout and I go back to the first picture it doesn't change anymore

public class MainActivity extends AppCompatActivity {

private Button button1;
private Button button2;
private Button changeLayout;
private Button exit;
private ImageView imageView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    button1 = findViewById(R.id.button1);
    button2 = findViewById(R.id.button2);
    imageView = findViewById(R.id.imageView);
    changeLayout = findViewById(R.id.changeLayoutBt);
    exit = findViewById(R.id.exitBtn);
}

public void changeImage(View view) {
    switch (view.getId()){
        case R.id.button1:
            imageView.setImageResource(R.drawable.orange);
            break;
        case R.id.button2:
            imageView.setImageResource(R.drawable.java);
            break;
    }
}

public void changeLayout(View view) {
    setContentView(R.layout.second_layout);
}

public void exit(View view) {
    setContentView(R.layout.activity_main);
}

} `

Answer 1

In order to create new layout got to File>New>Activity>Empty Activity Change your changeLayout code to this one

public void changeLayout() {
    startActivity(new Intent(MainActivity.this, Main2Activity.class);
}

Main2Activity.class is your newly created java class. It would be Main2Activity.java or what ever you named it.

Inside your onCreate() method. Just below

changeLayout = findViewById(R.id.changeLayoutBt);

Paste this code

changeLayout.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            changeLayout();
        }
    });