谁能告诉我如何打开一个特定的 fragment 来自另一个 Activity 按钮点击事件的 viewpager。

我正在使用一个显示两个选项的警告对话框 在 viewpager 中选择相应的屏幕，如下所示，但我得到的是 null 单击屏幕按钮上的指针，该按钮具有打开 viewpager 第二页的代码。

public class MainActivity extends FragmentActivity {
    int pos;
    ViewPager pager;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);     
         pager = (ViewPager) findViewById(R.id.viewPager);
        pager.setAdapter(new MyPagerAdapter(getSupportFragmentManager()));
      Button   ds = (Button) findViewById(R.id.show_back);
     ds.setOnClickListener(new OnClickListener() {

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

        }
     });
    }

    private class MyPagerAdapter extends FragmentPagerAdapter {

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

        @Override
        public Fragment getItem(int pos) {
            switch(pos) {

            case 0: return FirstFragment.newInstance("FirstFragment, Instance 1");
            case 1: return SecondFragment.newInstance("SecondFragment, Instance 1");
            default: return FirstFragment.newInstance("FirstFragment, Instance 1");
            }
        }

        @Override
        public int getCount() {
            return 2;
        }       
    }

goesBack = (Button) findViewById(R.id.show_front);
goesBack.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View v) {
        AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(SecondActivity.this, AlertDialog.THEME_DEVICE_DEFAULT_LIGHT);
        alertDialogBuilder.setMessage("Please choose your Favourite Screen");
        alertDialogBuilder.setNegativeButton("ScreenOne",new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
            Intent go = new Intent(SecondActivity.this,MainActivity.class);
            startActivity(go);
             }
        });
        alertDialogBuilder.setPositiveButton("ScreenTwo", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface arg0, int arg1) {
                // Create new fragment and transaction
                SecondFragment newFragment = new SecondFragment();
                FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
                transaction.replace(R.id.container, newFragment, "NewFragment");
                transaction.addToBackStack(null);
                transaction.commit();
             }
        });
        AlertDialog alertDialog = alertDialogBuilder.create();
        alertDialog.show();         
    }
});

感谢和问候，

阿迪亚.J

最佳答案

在您的 onClick 中，只需传递您想要在 intent 的 extra 中显示的 viewpager 的位置，然后在 viewpager Activity 中，只需调用 pager.setCurrentItem(position)。

所以你的 onClick 代码应该是这样的

goesBack = (Button) findViewById(R.id.show_front);
goesBack.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View v) {
        AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(SecondActivity.this, AlertDialog.THEME_DEVICE_DEFAULT_LIGHT);
        alertDialogBuilder.setMessage("Please choose your Favourite Screen");
        alertDialogBuilder.setNegativeButton("ScreenOne",new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                Intent go = new Intent(SecondActivity.this,MainActivity.class);

                // you pass the position you want the viewpager to show in the extra, 
                // please don't forget to define and initialize the position variable
                // properly
                go.putExtra("viewpager_position", 0)

                startActivity(go);
            }
        });
        alertDialogBuilder.setPositiveButton("ScreenTwo", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface arg0, int arg1) {
                // Create new fragment and transaction

                /*SecondFragment newFragment = new SecondFragment();
                FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
                transaction.replace(R.id.container, newFragment, "NewFragment");
                transaction.addToBackStack(null);
                transaction.commit();*/
                // You don't do the above code, it will just create a new fragment
                // you do this instead.
                Intent go = new Intent(SecondActivity.this,MainActivity.class);

                // you pass the position you want the viewpager to show in the extra, 
                // please don't forget to define and initialize the position variable
                // properly
                go.putExtra("viewpager_position", 1)

                startActivity(go);
             }
        });
        AlertDialog alertDialog = alertDialogBuilder.create();
        alertDialog.show();         
    }
});

您的 viewpager Activity 的代码应该是这样的。

int pos;
ViewPager pager;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);     
    int position = 0;
    Bundle extras = getIntent().getExtras();
    if(extras != null) {
        position = extras.getInt("viewpager_position");
    }
    pager = (ViewPager) findViewById(R.id.viewPager);
    MyPagerAdapter myPagerAdapter = new MyPagerAdapter(getSupportFragmentManager());
    pager.setAdapter(myPagerAdapter);
    Button   ds = (Button) findViewById(R.id.show_back);
    ds.setOnClickListener(new OnClickListener() {

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

    }
    });

    pager.setCurrentItem(position) // this way if there is no extras 
    // you will get first position of viewpager
    // otherwise you will get the position of viewpager whichever was passed in the intent.
}

关于android - 如何从另一个 Activity 按钮单击事件打开viewpager中的特定 fragment 页面，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33627106/