Question

我在后面的图标工具栏上遇到了问题，当我点击两次返回应用程序崩溃时null指针异常，在我的 getActivity（）上回忆错误.onBackPressed（）;

这是片段：

package com.example.android.evilsecretgallery;

import android.graphics.Bitmap;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.transition.TransitionInflater;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.bumptech.glide.Glide;
import com.bumptech.glide.request.target.SimpleTarget;
import com.bumptech.glide.request.transition.Transition;
import com.github.chrisbanes.photoview.PhotoView;


public class ImageDetailFragment extends Fragment {

    private static final String EXTRA_IMAGE = "image_item";
    private static final String EXTRA_TRANSITION_NAME = "transition_name";

    public ImageDetailFragment() {
        // Required empty public constructor
    }

    public static ImageDetailFragment newInstance(ImageModel image, String transitionName) {
        ImageDetailFragment fragment = new ImageDetailFragment();
        Bundle args = new Bundle();
        args.putParcelable(EXTRA_IMAGE, image);
        args.putString(EXTRA_TRANSITION_NAME, transitionName);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        postponeEnterTransition();
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            setSharedElementEnterTransition(TransitionInflater.from(getContext()).inflateTransition(android.R.transition.move));
        }

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_image_detail, container, false);

        Toolbar toolbar = getActivity().findViewById(R.id.toolbar);
        toolbar.setTitle(" ES     ");
        toolbar.setTitleTextAppearance(getActivity(), R.style.EvilTextAppearance);
        toolbar.setNavigationOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                getActivity().onBackPressed();
            }
        });
        return rootView;
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        final ImageModel image = getArguments().getParcelable(EXTRA_IMAGE);
        String transitionName = getArguments().getString(EXTRA_TRANSITION_NAME);

        final PhotoView imageView = view.findViewById(R.id.detail_image);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            imageView.setTransitionName(transitionName);
        }

        Glide.with(getActivity())
                .asBitmap()
                .load(image.getUrl())
                .into(new SimpleTarget<Bitmap>() {
                    @Override
                    public void onResourceReady(@NonNull Bitmap resource, @Nullable Transition<? super Bitmap> transition) {
                        startPostponedEnterTransition();
                        imageView.setImageBitmap(resource);
                    }
                });

    }

}

返回此活动：

package com.example.android.evilsecretgallery;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.view.MenuItem;

public class PagesActivity extends AppCompatActivity {

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

        Toolbar toolbar = findViewById(R.id.toolbar);
        toolbar.setTitle(" ES     ");
        toolbar.setTitleTextAppearance(this, R.style.EvilTextAppearance);
        setSupportActionBar(toolbar);

        if (getSupportActionBar()!=null){
            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
            getSupportActionBar().setDisplayShowHomeEnabled(true);
        }

        getSupportFragmentManager()
                .beginTransaction()
                .add(R.id.content, RecyclerViewFragment.newInstance())
                .commit();
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (item.getItemId()==android.R.id.home)
            finish();
        return super.onOptionsItemSelected(item);
    }
}

然后，如果我再次回到下面的这个活动，它会给我一个错误：

package com.example.android.evilsecretgallery;

import android.content.Intent;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    ImageView cover;
    Toolbar toolbar;

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

        toolbar = findViewById(R.id.toolbar);
        toolbar.setTitle(" ES     ");
        toolbar.setTitleTextAppearance(this, R.style.EvilTextAppearance);
        setSupportActionBar(toolbar);

        cover = findViewById(R.id.cover_id);
        cover.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // Create a new intent to open the PagesActivity
                Intent intent = new Intent(MainActivity.this, PagesActivity.class);
                // Start the new activity
                startActivity(intent);
            }
        });

        Button siteButton = findViewById(R.id.site_button);
        siteButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                String url = "http://www.evilsecret.it";

                Intent intent = new Intent(Intent.ACTION_VIEW);
                intent.setData(Uri.parse(url));
                startActivity(intent);
            }
        });
    }
}

我做了一些实验，如果我从页面活动回来，它没有问题。我必须在片段中使用不同的方法吗？

Answer 1

尝试clean和rebuild您的项目

它对我有用。

FragmentActivity.onBackPressed（）上的NullPointerException

1 个答案: