在我的主要活动屏幕上，我有一个按钮，可以将我带到另一个屏幕。但当我点击我的应用程序崩溃，我收到一个错误。
java.lang.RuntimeException：无法启动活动ComponentInfo {com.app.appname / com.app.appname.view}：java.lang.NullPointerException
蓝色下划线位于此行的view.java：
ArrayList spinnerArrayList = bundle.getIntegerArrayList（“arraylist”）;
这是我的完整view.java代码：
public class view extends AppCompatActivity {
private LinearLayout mLinearLayout;
private ArrayList<SearchableSpinner> mSpinners;
private List<AppCompatButton> mButtons = new ArrayList<>();
private List<CheckBox> mCheckboxes = new ArrayList<>();
private List<TextView> mTextviews = new ArrayList<>();
private List<EditText> mEdittexts = new ArrayList<>();
private List<View> mViews = new ArrayList<>();
private Map<String, String> numberItemValues = new HashMap<>();
List<String> itemList = new ArrayList<>();
private Spinner spinner;
private TextView textview;
private CheckBox checkbox;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_create);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
GlobalClass globalClass = (GlobalClass) this.getApplicationContext();
textview = findViewById(R.id.textview);
checkbox = findViewById(R.id.checkbox);
ArrayList<String> items = new ArrayList<>();
items.add(String.valueOf(mSpinners)); // add you selected item
globalClass.setItems(items);
mSpinners = new ArrayList<>();
mLinearLayout = findViewById(R.id.my_linearLayout);
findViewById(R.id.my_linearLayout).requestFocus();
Intent gotIntent = getIntent();
Bundle bundle = getIntent().getBundleExtra("extraBundle");
ArrayList<Integer> spinnerArrayList = bundle.getIntegerArrayList("arraylist");
//creating a for loop, to create the number of spinners in the spinnerarray list size
for(int i = 0; i < spinnerArrayList.size(); i++) {
final Spinner spinner = makeSpinner();
mLinearLayout.addView(spinner);
final View newView = makeView();
//Add a new view
mLinearLayout.addView(newView);
mViews.add(newView);
final EditText newEdittext = makeEdittext();
mLinearLayout.addView(newEdittext);
mEdittexts.add(newEdittext);
final CheckBox newCheckbox = makeCheckbox();
mLinearLayout.addView(newCheckbox);
//TODO add checkbox to your list
mCheckboxes.add(newCheckbox);
final TextView newTextview = makeTextview();
mLinearLayout.addView(newTextview);
mTextviews.add(newTextview);
newCheckbox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
// makes the set disappear when checkbox is ticked.
newCheckbox.setVisibility(View.VISIBLE);
spinner.setVisibility(View.VISIBLE);
newView.setVisibility(View.VISIBLE);
newEdittext.setVisibility(View.VISIBLE);
newTextview.setVisibility(View.VISIBLE);
//textview.setVisibility(View.VISIBLE);
newCheckbox.animate().alpha(0.0f).setDuration(1000).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
newCheckbox.setVisibility(View.GONE);
}
});
spinner.animate().alpha(0.0f).setDuration(1000).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
spinner.setVisibility(View.GONE);
}
});
newView.animate().alpha(0.0f).setDuration(1000).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
newView.setVisibility(View.GONE);
}
});
newEdittext.animate().alpha(0.0f).setDuration(1000).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
newEdittext.setVisibility(View.GONE);
}
});
newTextview.animate().alpha(0.0f).setDuration(1000).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
newTextview.setVisibility(View.GONE);
}
});
}
});
//TODO Add the spinner on item selected listener to get selected items
spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parentView, View selectedItemView, int position, long id) {
String currentItem = itemList.get(position);
String aisleNumber = numberItemValues.get(currentItem);
//TODO you can use the above aisle number to add to your text view
//mTextviews.get(mTextviews.size() -1).setText(aisleNumber);
newTextview.setText(aisleNumber);
}
@Override
public void onNothingSelected(AdapterView<?> parentView) {
// code here
}
});
final int listSize = mViews.size();
//code for deleting the said item.
newView.setOnClickListener(new View.OnClickListener() {
//start
@Override
public void onClick(View view) {
//when the 'new button' is pressed, alert shows if you are sure you want to delete the item or not.
final View.OnClickListener context = this;
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(view.this);
// set title
alertDialogBuilder.setTitle("Delete Item");
// set dialog message
alertDialogBuilder
.setMessage("Are you sure you want to delete this item?")
.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// if this button is clicked, close
// current activity
if (listSize > 0) {
mCheckboxes.get(listSize - 1).setVisibility(View.GONE);
mSpinners.get(listSize - 1).setVisibility(View.GONE);
mViews.get(listSize - 1).setVisibility(View.GONE);
mTextviews.get(listSize - 1).setVisibility(View.GONE);
mEdittexts.get(listSize - 1).setVisibility(View.GONE);
Toast.makeText(getBaseContext(), "Item removed.", Toast.LENGTH_SHORT).show();
}
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// if this button is clicked, just close
// the dialog box and do nothing
dialog.cancel();
}
});
// create alert dialog
AlertDialog alertDialog = alertDialogBuilder.create();
// show it
alertDialog.show();
}
});
//setting spinner selection values
int positionOfSpinner = spinnerArrayList.get(i);
spinner.setSelection(positionOfSpinner);
}
//code for the add button to add more items
FloatingActionButton floatingActionButton =
(FloatingActionButton) findViewById(R.id.fab);
floatingActionButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Toast.makeText(getBaseContext(), "Item added!", Toast.LENGTH_SHORT).show();
spinner = findViewById(R.id.spinner);
mLinearLayout.setVisibility(View.VISIBLE);
// Handle ze click.
final Spinner spinner = makeSpinner();
mLinearLayout.addView(spinner);
LinearLayout.LayoutParams layoutParams = (LinearLayout.LayoutParams) spinner.getLayoutParams();
layoutParams.setMargins(5, 100, 10, 0); //top 70
Resources resources = getResources();
DisplayMetrics metrics = resources.getDisplayMetrics();
layoutParams.height = (int) (70 * ((float) metrics.densityDpi / DisplayMetrics.DENSITY_DEFAULT)); //80
layoutParams.width = (int) (240 * ((float) metrics.densityDpi / DisplayMetrics.DENSITY_DEFAULT)); //240
spinner.setLayoutParams(layoutParams);
final View newView = makeView();
//Add a new view
mLinearLayout.addView(newView);
mViews.add(newView);
final EditText newEdittext = makeEdittext();
mLinearLayout.addView(newEdittext);
mEdittexts.add(newEdittext);
final int listSize = mViews.size();
//code for deleting the said item.
//code for deleting the said item.
newView.setOnClickListener(new View.OnClickListener() {
//start
@Override
public void onClick(View view) {
//when the 'new button' is pressed, alert shows if you are sure you want to delete the item or not.
final View.OnClickListener context = this;
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(view.this);
// set title
alertDialogBuilder.setTitle("Delete Item");
// set dialog message
alertDialogBuilder
.setMessage("Are you sure you want to delete this item?")
.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// if this button is clicked, close
// current activity
//final int listSize = mViews.size();
if (listSize > 0) {
mCheckboxes.get(listSize - 1).setVisibility(View.GONE);
mSpinners.get(listSize - 1).setVisibility(View.GONE);
mViews.get(listSize - 1).setVisibility(View.GONE);
mTextviews.get(listSize - 1).setVisibility(View.GONE);
mEdittexts.get(listSize - 1).setVisibility(View.GONE);
Toast.makeText(getBaseContext(), "Item removed.", Toast.LENGTH_SHORT).show();
}
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// if this button is clicked, just close
// the dialog box and do nothing
dialog.cancel();
}
});
// create alert dialog
AlertDialog alertDialog = alertDialogBuilder.create();
// show it
alertDialog.show();
}
});
//Add a new checkbox
final CheckBox newCheckbox = makeCheckbox();
mLinearLayout.addView(newCheckbox);
//TODO add checkbox to your list
mCheckboxes.add(newCheckbox);
newCheckbox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
// makes the set disappear when checkbox is ticked.
newCheckbox.setVisibility(View.VISIBLE);
spinner.setVisibility(View.VISIBLE);
newView.setVisibility(View.VISIBLE);
newEdittext.setVisibility(View.VISIBLE);
//textview.setVisibility(View.VISIBLE);
newCheckbox.animate().alpha(0.0f).setDuration(1000).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
newCheckbox.setVisibility(View.GONE);
}
});
spinner.animate().alpha(0.0f).setDuration(1000).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
spinner.setVisibility(View.GONE);
}
});
newView.animate().alpha(0.0f).setDuration(1000).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
newView.setVisibility(View.GONE);
}
});
newEdittext.animate().alpha(0.0f).setDuration(1000).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
newEdittext.setVisibility(View.GONE);
}
});
/* textview.animate().alpha(0.0f).setDuration(1000).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
textview.setVisibility(View.GONE);
}
});*/
}
});
final TextView newTextview = makeTextview();
mLinearLayout.addView(newTextview);
mTextviews.add(newTextview);
//TODO Add the spinner on item selected listener to get selected items
spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parentView, View selectedItemView, int position, long id) {
String currentItem = itemList.get(position);
String aisleNumber = numberItemValues.get(currentItem);
//TODO you can use the above aisle number to add to your text view
//mTextviews.get(mTextviews.size() -1).setText(aisleNumber);
newTextview.setText(aisleNumber);
}
@Override
public void onNothingSelected(AdapterView<?> parentView) {
// code here
}
});
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.create_menu, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
Intent startSettingsActivity = new Intent(this, settings.class);
startActivity(startSettingsActivity);
//start the settings activity here.
return true;
}
/* else if (id == R.id.action_delete) {
for(int j=0; j<mCheckboxes.size(); j++){
mCheckboxes.get(j).setVisibility(View.GONE);
}
for(int j=0; j<mSpinners.size(); j++){
mSpinners.get(j).setVisibility(View.GONE);
}
for(int j=0; j<mViews.size(); j++){
mViews.get(j).setVisibility(View.GONE);
}
for(int j=0; j<mTextviews.size(); j++){
mTextviews.get(j).setVisibility(View.GONE);
}
for(int j=0; j<mEdittexts.size(); j++){
mEdittexts.get(j).setVisibility(View.GONE);
}
Toast.makeText(getBaseContext(), "List removed.", Toast.LENGTH_SHORT).show();
return true;
}*/
else if (id ==R.id.action_help) {
// setup the alert builder
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Help");
builder.setMessage("To use this app, first go to Create your Shopping List.\n" +
"Here, you can add items to your list. Once you have added all items, you can click the menu at the top right corner (or if it doesnt appear press your menu button beside your home button on your device, then click View your List.\n" +
"This will take you to the screen where you can view you shopping list with the items in aisle order to make your shop much easier.\n" +
"You can still add items at this point. Press the white background of each item to delete the item if you wish.");
// add a button
builder.setPositiveButton("OK", null);
// create and show the alert dialog
AlertDialog dialog = builder.create();
dialog.show();
return true;
}
return super.onOptionsItemSelected(item);
}
//use a relative layout and specify which ones are to layout_toRightOf and layout_below
//DUPLICATING ITEMS WHEN FAB IS PRESSED//
private CheckBox makeCheckbox() {
//Create new Checkbox
CheckBox checkbox = new CheckBox(this);
// Setup layout
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.MATCH_PARENT,
LinearLayout.LayoutParams.WRAP_CONTENT);
//setup relative layout for the positioning of the objects
Resources resources = getResources();
DisplayMetrics metrics = resources.getDisplayMetrics();
RelativeLayout.LayoutParams relativeParams = new RelativeLayout.LayoutParams((int) (70 * ((float) metrics.densityDpi / DisplayMetrics.DENSITY_DEFAULT)), (int) (240 * ((float) metrics.densityDpi / DisplayMetrics.DENSITY_DEFAULT)));
relativeParams.addRule(RelativeLayout.RIGHT_OF, R.id.textview);
checkbox.setLayoutParams(relativeParams);
// RelativeLayout.LayoutParams relativeParams = new RelativeLayout.LayoutParams(relativeParams.addRule(RelativeLayout.RIGHT_OF, R.id.textview));
checkbox.setLayoutParams(layoutParams);
return checkbox;
}
private TextView makeTextview() {
//create new textview
TextView textview = new TextView(this);
//setup layout
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.MATCH_PARENT,
LinearLayout.LayoutParams.WRAP_CONTENT);
textview.setLayoutParams(layoutParams);
textview.setTextSize(30);
return textview;
}
private EditText makeEdittext() {
//create new edittext
EditText edittext = new EditText(this);
//setup layout
final LinearLayout.LayoutParams lparams = new LinearLayout.LayoutParams(50, 50); // Width , height
edittext.setLayoutParams(lparams);
edittext.setInputType(InputType.TYPE_CLASS_NUMBER | InputType.TYPE_NUMBER_FLAG_DECIMAL | InputType.TYPE_NUMBER_FLAG_SIGNED);
edittext.setHint("qty");
return edittext;
}
private View makeView() {
//create new View
View view = new View(this);
view.setBackgroundColor(Color.parseColor("#ffffff"));
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams( LinearLayout.LayoutParams.MATCH_PARENT, 100);
new LinearLayout.LayoutParams( LinearLayout.LayoutParams.WRAP_CONTENT, 50);
//LinearLayout.LayoutParams.MATCH_PARENT,
// LinearLayout.LayoutParams.WRAP_CONTENT);
view.setClickable(true);
view.setLayoutParams(layoutParams);
//setup layout
return view;
}
private Spinner makeSpinner() {
//opens csv
InputStream inputStream = getResources().openRawResource(R.raw.shopitems);
CSVFile csvFile = new CSVFile(inputStream);
//TODO I made this variable global, declared it at the very top of this file
itemList = csvFile.read();
//Create new spinner
// SearchableSpinner spinner = (SearchableSpinner) new Spinner(this, Spinner.MODE_DROPDOWN);
SearchableSpinner spinner = new SearchableSpinner(this);
// Setup layout
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.MATCH_PARENT,
LinearLayout.LayoutParams.WRAP_CONTENT);
spinner.setLayoutParams(layoutParams);
MyListAdapter adapter = new MyListAdapter(this, R.layout.listrow, R.id.txtid, itemList);
spinner.setAdapter(adapter);
//Add it to your list of spinners so you can retrieve their data when you click the getSpinner button
mSpinners.add(spinner);
return spinner;
}
private class CSVFile {
InputStream inputStream;
public CSVFile(InputStream inputStream) {
this.inputStream = inputStream;
}
public List<String> read() {
List<String> resultList = new ArrayList<String>();
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
try {
String line;
while ((line = reader.readLine()) != null) {
String[] row = line.split(",");
//TODO I edited this part so that you'd add the values in our new hash map variable
numberItemValues.put(row[1], row[0]);
resultList.add(row[1]);
}
} catch (IOException e) {
Log.e("Main", e.getMessage());
} finally {
try {
inputStream.close();
} catch (IOException e) {
Log.e("Main", e.getMessage());
}
}
return resultList;
}
}}
create.java意图部分
//takes the size of the list of spinners, for reference
ArrayList<Integer> spinnerList = new ArrayList<>();
for(int i = 0; i < mSpinners.size(); i++) {
spinnerList.add(mSpinners.get(i).getSelectedItemPosition());
}
Bundle newBundle = new Bundle();
newBundle.putIntegerArrayList("arraylist", spinnerList);
Intent newIntent = new Intent(create.this, viewscreen.class);
newIntent.putExtra("extraBundle", newBundle);
你可以使用put arraylist值
Bundle bundle = new Bundle();
bundle.putParcelableArrayList("arraylist", arraylist);
并使用如下代码获得arraylist值
Bundle extras = getIntent().getExtras();
extras.getParcelableArrayList("arraylist");
检查主活动按钮单击方法中的代码，确保正确放入包和数据。并在视图活动中，建议写这样的：
Bundle bundle = getIntent().getBundleExtra("extraBundle");
if (bundle!=null) {
if(bundle.containsKey("arraylist") {
ArrayList<Integer> spinnerArrayList = bundle.getIntegerArrayList("arraylist");
//do something
}
} else {
//log error info
}
Intent gotIntent = getIntent();
Bundle bundle = getIntent().getBundleExtra("extraBundle");
please print bundle. because the bundle is null then an exception is created
for example:-
send data:-
String[] _string=new String[2];
_string[0]="MONDAY";
_string[1]="TUESDAY";
Intent _intent = new Intent(this, second.class);
Bundle bundle = new Bundle();
_intent .putExtra("strings", myStrings);
_intent .putExtras(bundle);
startActivity(_intent );
receive data:-
Intent i = getIntent();
Bundle extras=i.getExtras();
if(extras != null) //this line is necessary for getting any value
{
String[] _Values = i.getStringArrayExtra("strings");
Toast.makeText(this, "value="+_Values [0]+""+_Values [1], Toast.LENGTH_SHORT).show();
}
尝试检查空值。也许intent是null或者你传入它的bundle是null
Intent gotIntent = getIntent();
if ((gotIntent != null) && (gotIntent.getBundleExtra("extraBundle") != null)) {
Bundle bundle = gotIntent.getBundleExtra("extraBundle");
if(bundle.containsKey("arraylist") {
ArrayList<Integer> spinnerArrayList = bundle.getIntegerArrayList("arraylist");
}
}
尝试获取如下所示的包： -
Intent gotIntent = getIntent();
Bundle bundle = gotIntent.getExtras();
ArrayList<Integer> spinnerArrayList = bundle.getIntegerArrayList("arraylist");
methodgetBundleExtra("String")获取名为String的包。当getExtras()得到一个包含放入数组中的所有项目的包。用putExtra(Bundle bundle, String tag)放置你的包，这样getBundleExtra(String tag)将返回该值。
要检查null，
if(gotIntent != null && gotIntent.hasExtra("bundleExtras")){
Bundle bundle = gotIntent.getExtras();
ArrayList<Integer> spinnerArrayList = bundle.getIntegerArrayList("arraylist");
}
确保您已在清单中初始化您的活动
并直接使用这样的
ArrayList<Integer> list = getIntent.getIntegerArrayListExtra("")