这真的很正常，很多时候都会问问题，但我仍然无法问它。我的应用程序崩溃没有任何错误。整个应用程序似乎很好，它的源代码没有任何错误，但仍然是应用程序崩溃。
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.squareup.picasso.Picasso;
public class HomePage extends AppCompatActivity {
private RecyclerView mblogList;
private DatabaseReference mdatabase;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mdatabase= FirebaseDatabase.getInstance().getReference().child("Blog");
setContentView(R.layout.activity_home_page);
mblogList=(RecyclerView)findViewById(R.id.blog_list);
mblogList.setHasFixedSize(true);
mblogList.setItemViewCacheSize(20);
mblogList.setDrawingCacheEnabled(true);
mblogList.setDrawingCacheQuality(View.DRAWING_CACHE_QUALITY_HIGH);
mblogList.setLayoutManager(new LinearLayoutManager(this));
}
@Override
protected void onStart() {
super.onStart();
FirebaseRecyclerAdapter<Blog,BlogViewHolder>firebaseRecyclerAdapter=new FirebaseRecyclerAdapter<Blog, BlogViewHolder>(Blog.class,R.layout.blog_row,BlogViewHolder.class,mdatabase) {
@Override
protected void populateViewHolder(BlogViewHolder viewHolder, Blog model, int position) {
viewHolder.setTitle(model.getTitle());
viewHolder.setDesc(model.getDescription());
viewHolder.setImage(getApplicationContext(),model.getImage());
}
};
mblogList.setAdapter(firebaseRecyclerAdapter);
}
public static class BlogViewHolder extends RecyclerView.ViewHolder {
View mView;
public BlogViewHolder(View itemView) {
super(itemView);
mView=itemView;
}
public void setTitle(String title){
TextView post_title=(TextView)mView.findViewById(R.id.post_title);
post_title.setText(title);
}
public void setDesc(String desc){
TextView post_title=(TextView)mView.findViewById(R.id.post_des);
post_title.setText(desc);
}
public void setImage(Context ctx,String image){
ImageView post_image=(ImageView)mView.findViewById(R.id.post_image);
Picasso.with(ctx).load(image).into(post_image);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.action_menu,menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId()==R.id.action_add){
startActivity(new Intent(HomePage.this,BlogPost.class));
}
return super.onOptionsItemSelected(item);
}
}
这是homeActivity。这很明显。
< activity android:name=".HomePage"
android:exported="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".BlogPost">
<intent-filter>
<action android:name="android.intent.action.GET_CONTENT">
<category android:name="android.intent.category.DEFAULT" />
</action>
</intent-filter>
</activity>
<activity android:name=".LoginActivity"
android:exported="true"/>
实际上我想首先打开loginActivity，我尝试用HomePage活动更改名称，但它仍然崩溃。我不知道为什么会发生这种情况。我已经尝试过各种可能的方法，尝试清理和重建项目 错误就在这里
05-16 17:41:37.992 7012-7012/com.example.hp.urblog E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.hp.urblog, PID: 7012
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.hp.urblog/com.example.hp.urblog.LoginActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.os.Looper android.content.Context.getMainLooper()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2327)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.os.Looper android.content.Context.getMainLooper()' on a null object reference
at android.content.ContextWrapper.getMainLooper(ContextWrapper.java:102)
at com.google.android.gms.common.api.GoogleApiClient$Builder.<init>(Unknown Source)
at com.example.hp.urblog.LoginActivity.<init>(LoginActivity.java:20)
at java.lang.Class.newInstance(Native Method)
at android.app.Instrumentation.newActivity(Instrumentation.java:1067)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2317)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
这是我的loginActivity
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import com.google.android.gms.auth.api.Auth;
import com.google.android.gms.auth.api.signin.GoogleSignInAccount;
import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
import com.google.android.gms.auth.api.signin.GoogleSignInResult;
import com.google.android.gms.common.api.GoogleApiClient;
public class LoginActivity extends AppCompatActivity {
private Button Sign_in_button;
private static final int RC_SIGN_IN = 9001;
GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
.requestEmail()
.build();
GoogleApiClient mGoogleApiClient = new GoogleApiClient.Builder(this)
// .enableAutoManage(LoginActivity.this, MainActivity.class)
.addApi(Auth.GOOGLE_SIGN_IN_API, gso)
.build();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
Sign_in_button=(Button)findViewById(R.id.sign_in_button);
Sign_in_button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.sign_in_button:
signIn();
break;
// ...
}
}
});
}
private void signIn() {
Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient );
startActivityForResult(signInIntent, RC_SIGN_IN);
}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
// Result returned from launching the Intent from GoogleSignInApi.getSignInIntent(...);
if (requestCode == RC_SIGN_IN) {
GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
handleSignInResult(result);
}
}
private void handleSignInResult(GoogleSignInResult result) {
//Log.d(TAG, "handleSignInResult:" + result.isSuccess());
if (result.isSuccess()) {
// Signed in successfully, show authenticated UI.
GoogleSignInAccount acct = result.getSignInAccount();
startActivity(new Intent(this,MainActivity.class));
// mStatusTextView.setText(getString(R.string.signed_in_fmt, acct.getDisplayName()));
// updateUI(true);
} //else {
// Signed out, show unauthenticated UI.
// updateUI(false);
//}
}
}
答案 0 :(得分：0)
Yup得到您的问题GoogleApiClient未正确初始化
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
.requestEmail()
.build();
GoogleApiClient mGoogleApiClient = new GoogleApiClient.Builder(LoginActivity.this)
// .enableAutoManage(LoginActivity.this, MainActivity.class)
.addApi(Auth.GOOGLE_SIGN_IN_API, gso)
.build();
Sign_in_button=(Button)findViewById(R.id.sign_in_button);
Sign_in_button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.sign_in_button:
signIn();
break;
// ...
}
}
});
}
参考 - https://stackoverflow.com/a/41320391/4741746和https://stackoverflow.com/a/28928746/4741746
每当你想要传递上下文时，还有一个建议总是使用ActivityName.this，比如LoginActivity.this不仅仅是＃34;这个＆＃34;