Question

在我的应用程序中，当我按下以下活动的后退按钮时，不会返回主要活动（片段）但应用程序关闭。

public class ListaSmartphone extends AppCompatActivity {

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

    Button buttonSP = (Button)findViewById(R.id.buttonXIAOMI);
    buttonSP.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View arg0) {
            Intent openListaSP = new Intent(ListaSmartphone.this, ElencoXiaomi.class);
            startActivity(openListaSP);
        }
    });

    Button buttonTB = (Button)findViewById(R.id.buttonMEIZU);
    buttonTB.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View arg0) {
            Intent openListaTB = new Intent(ListaSmartphone.this, ElencoMeizu.class);
            startActivity(openListaTB);
        }
    });

}
}

这是主要的活动代码

public class MainActivity extends AppCompatActivity {

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

    ViewPager vpPager = (ViewPager) findViewById(R.id.vpPager);
    adapterViewPager = new MyPagerAdapter(getSupportFragmentManager());
    vpPager.setAdapter(adapterViewPager);
    vpPager.setPageTransformer(true, new RotateUpTransformer());

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}


public static class MyPagerAdapter extends FragmentPagerAdapter {
    private static int NUM_ITEMS = 4;
    private static final String[] TAB_TITLES = new String[]{"WOW STORE", "PRODOTTI", "SERVIZI", "INFO"};

    public MyPagerAdapter(FragmentManager fragmentManager) {
        super(fragmentManager);
    }

    // Returns total number of pages

    // Returns the fragment to display for that page
    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return FragmentWithZeroImage.newInstance("", R.drawable.wowstorelogo);
            case 1:
                return FragmentWithOneImage.newInstance("", R.drawable.prodotti);
            case 2:
                return FragmentWithTwoImages.newInstance("", R.drawable.riparazioni);
            case 3:
                return FragmentWithThreeImages.newInstance("", R.drawable.info);
            default:
                return null;
        }
    }

    @Override
    public int getCount(){
        return TAB_TITLES.length;
    }

    @Override
    public CharSequence getPageTitle(int position){
        return TAB_TITLES[position];
    }


}

}

应用程序工作正常，没有错误，但在按下后退按钮的设备上，应用程序退出并且不会返回到MainActivity。我使用Main Activity和四个片段。

Answer 1

在传递意图时你可能使用了finish（）;在startActivity（）

之后

Answer 2

使用此代码：

 @Override
public void onBackPressed() {
     this.startActivity(new Intent(ListaSmartphone.this,MainActivity.class));
// super.onBackPressed();

 }

并在MainActivity的onCreate函数中打开片段

Answer 3

如果您想返回按返回按钮上的MainActivity，请使用此代码

@Override
public void onBackPressed() {
 startActivity(new Intent(getApplicationContext(),MainActivity.class));
}

当按下后退按钮时，APP退出。为什么？

3 个答案: