1
所以我試圖從我的Firebase數據庫收集數據，將它存儲在ArrayList中，將該ArrayList轉換爲Object數組，然後將其轉換到一個字符串數組。我需要將對象數組轉換爲字符串數組，但它不斷返回空指針
我的代碼非常有效，直到我嘗試將我的ArrayList轉換爲對象數組，然後我得到一個空指針。
public class PostSkillsActivity extends AppCompatActivity {
ArrayList<String> skills_array;
Object[] mySkills;
public String[] skills;
private AutoCompleteTextView jobInputSkills;
private Button finishBtn;
private ImageButton addSkillsBtn;
private GridView gridView;
private DatabaseReference mDatabaseSkills;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_post_skills);
mDatabaseSkills = FirebaseDatabase.getInstance().getReference().child("Skills");
mDatabaseSkills.keepSynced(true);
mDatabaseSkills.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
collectSkills((Map<String,Object>) dataSnapshot.getValue());
}
@Override
public void onCancelled(DatabaseError databaseError) {}
});
jobInputSkills = (AutoCompleteTextView) findViewById(R.id.input_job_skills);
finishBtn = (Button) findViewById(R.id.skills_finish_btn);
addSkillsBtn = (ImageButton) findViewById(R.id.add_skills_btn);
addSkillsBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
didTapButton(v);
addSkill();
}
});
/**
* Populate Skills Auto Text View
*/
mySkills = skills_array.toArray();
skills = Arrays.copyOf(mySkills, mySkills.length, String[].class);;
ArrayAdapter<String> adapter = new ArrayAdapter<String>
(this, android.R.layout.simple_list_item_1, skills);
jobInputSkills.setAdapter(adapter);
/**
* GridView Functionality
*/
gridView = (GridView) findViewById(R.id.gridview);
gridView.setAdapter(new SkillsAdapter(this, skills));
gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Toast.makeText(
getApplicationContext(),
((TextView) view.findViewById(R.id.label))
.getText(), Toast.LENGTH_SHORT).show();
}
});
}
private void collectSkills(Map<String,Object> skills) {
skills_array = new ArrayList<>();
Iterator myVeryOwnIterator = skills.keySet().iterator();
while(myVeryOwnIterator.hasNext()) {
String key=(String)myVeryOwnIterator.next();
String value=(String)skills.get(key);
skills_array.add(value);
}
}
private void addSkill() {
String[] words = jobInputSkills.getText().toString().split(" ");
StringBuilder sb = new StringBuilder();
if (words[0].length() > 0) {
sb.append(Character.toUpperCase(words[0].charAt(0)) + words[0].subSequence(1, words[0].length()).toString().toLowerCase());
for (int i = 1; i < words.length; i++) {
sb.append(" ");
sb.append(Character.toUpperCase(words[i].charAt(0)) + words[i].subSequence(1, words[i].length()).toString().toLowerCase());
}
}
final String skill_name = sb.toString();
if(!TextUtils.isEmpty(skill_name)){
final DatabaseReference newSkill = mDatabaseSkills.child(skill_name);
newSkill.child(skill_name).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
}
else {
newSkill.setValue(skill_name);
}
}
@Override
public void onCancelled(DatabaseError databaseError) {}
});
}
}
public void didTapButton(View view) {
ImageButton button = (ImageButton)findViewById(R.id.add_skills_btn);
final Animation myAnim = AnimationUtils.loadAnimation(this, R.anim.bounce);
// Use bounce interpolator with amplitude 0.2 and frequency 20
MyBounceInterpolator interpolator = new MyBounceInterpolator(0.2, 20);
myAnim.setInterpolator(interpolator);
button.startAnimation(myAnim);
}
public class SkillsAdapter extends BaseAdapter {
private Context context;
private final String[] skillValues;
public SkillsAdapter(Context context, String[] skillValues) {
this.context = context;
this.skillValues = skillValues;
}
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View gridView;
if (convertView == null) {
gridView = new View(context);
// get layout from mobile.xml
gridView = inflater.inflate(R.layout.skills_item, null);
// set value into textview
TextView textView = (TextView) gridView
.findViewById(R.id.label);
textView.setText(skillValues[position]);
// set image based on selected text
ImageView imageView = (ImageView) gridView
.findViewById(R.id.remove_skill_btn);
String skill = skillValues[position];
} else {
gridView = (View) convertView;
}
return gridView;
}
@Override
public int getCount() {
return skillValues.length;
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
}
}
這是我的Firebase數據庫。我需要將數組中的所有值存儲在數組中以填充AutoTextView。
Skills:
Android:"Android"
C++ Programming:"C++ Programming"
Carpentry:"Carpentry"
Electrician:"Electrician"
HTML:"HTML"
Housework:"Housework"
更新： 錯誤是與
mySkills = skills_array.toArray();
的skills_array開始應該從功能上包含的值
private void collectSkills(Map<String,Object> skills) {
skills_array = new ArrayList<>();
Iterator myVeryOwnIterator = skills.keySet().iterator();
while(myVeryOwnIterator.hasNext()) {
String key=(String)myVeryOwnIterator.next();
String value=(String)skills.get(key);
skills_array.add(value);
}
}
我是下面的日誌線78。
02-21 20:34:32.647 4153-4153/com.example.android.oddjobs E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.android.oddjobs, PID: 4153
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.oddjobs/com.example.android.oddjobs.PostSkillsActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object[] java.util.ArrayList.toArray()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2572)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2654)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1488)
at android.os.Handler.dispatchMessage(Handler.java:111)
at android.os.Looper.loop(Looper.java:207)
at android.app.ActivityThread.main(ActivityThread.java:5728)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:679)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object[] java.util.ArrayList.toArray()' on a null object reference
at com.example.android.oddjobs.PostSkillsActivity.onCreate(PostSkillsActivity.java:78)
at android.app.Activity.performCreate(Activity.java:6301)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1113)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2519)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2654)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1488)
at android.os.Handler.dispatchMessage(Handler.java:111)
at android.os.Looper.loop(Looper.java:207)
at android.app.ActivityThread.main(ActivityThread.java:5728)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:679)
02-21 20:34:34.022 4153-4239/com.example.android.oddjobs
E/NativeCrypto: ssl=0xaf9bb6c0 cert_verify_callback x509_store_ctx=0x9a87820c arg=0x0
02-21 20:34:34.022 4153-4239/com.example.android.oddjobs E/NativeCrypto: ssl=0xaf9bb6c0 cert_verify_callback calling verifyCertificateChain authMethod=ECDHE_RSA
請添加堆棧跟蹤。 – markers
感謝您的評論。我只是修復了這個帖子。 –
什麼是PostSkillsActivity.java的第78行？ –