意图putExtra错误，NullPointerException

Question

当我将信息从一项活动转移到另一项延误错误时，我做了笔记本

第一个活动（listView和按钮）-

public class ContactActivity extends Activity {

private ListView listContact;
private ArrayList<String> contacts;
private Intent intentContant;
private boolean sendText;
private Bundle bundle;
private String getContent;

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

    bundle = getIntent().getBundleExtra("android.intent.extra.INTENT");
    sendText = bundle.getBoolean("SetNewText");

    if(sendText){
        Intent intent = getIntent();
        getContent = intent.getStringExtra("FromAddEditString");
        contacts.add(getContent);
    }

    listContact = (ListView) findViewById(R.id.list_contact);

    intentContant = new Intent(ContactActivity.this, AddEditActivity.class);

    contacts = new ArrayList<String>();

    ArrayAdapter<String> contAdapter = new ArrayAdapter<String>(ContactActivity.this,
                                                            R.layout.list_item,
                                                            contacts);
    listContact.setAdapter(contAdapter);

    listContact.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            intentContant.putExtra("ContactName", parent.getAdapter().getItem(position).toString());

            bundle = new Bundle();
            bundle.putBoolean("ImportContact", true);
            intentContant.putExtra("android.intent.extra.INTENT", bundle);
            startActivity(intentContant);
        }
    });
}

public void onClick(View v){
    switch(v.getId()){
        case R.id.btnAdd:
            intentContant.putExtra("ContactName", "");

            bundle = new Bundle();
            bundle.putBoolean("ImportContact", false);
            intentContant.putExtra("android.intent.extra.INTENT", bundle);
            startActivity(intentContant);
            break;
        case R.id.btnBack:
            intentContant = new Intent(ContactActivity.this, MainActivity.class);
            startActivity(intentContant);
            break;
    }
}

}

第二项活动（编辑/添加联系人）

public class AddEditActivity extends Activity {

    private String result;
    private Boolean resultBoolean;
    private EditText editText;
    private Bundle extras;
    private Bundle extrasBoolean;

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

        extras = getIntent().getExtras();

        extrasBoolean = getIntent().getBundleExtra("android.intent.extra.INTENT");
        resultBoolean = extrasBoolean.getBoolean("ImportContact");

        editText = (EditText) findViewById(R.id.etAddEdit);

        if(resultBoolean) {
            result = extras.getString("ContactName");
            editText.setText(result);
        } else if(!resultBoolean)
            editText.setText("");

    }

    public void add_edit_click(View v){
        Bundle btnAccept = new Bundle();
        Intent intentAddEdit1 = new Intent(AddEditActivity.this, ContactActivity.class);
        Intent intentAddEdit2 = new Intent(AddEditActivity.this, ContactActivity.class);
        switch (v.getId()){
            case R.id.btnAccept:
                if (editText.getText().length() == 0)
                    Toast.makeText(getApplicationContext(), "Введите текст", Toast.LENGTH_SHORT).show();
                else {
                    btnAccept.putBoolean("SetNewText", true);
                    intentAddEdit1.putExtra("android.intent.extra.INTENT", btnAccept);

                    String result = editText.getText().toString();
                    intentAddEdit2.putExtra("FromAddEditString", result);
                    startActivity(intentAddEdit1);
                }
                break;
            case R.id.btnCancel:
                    btnAccept.putBoolean("SetNewText", false);
                    intentAddEdit1.putExtra("android.intent.extra.INTENT", btnAccept);
                    startActivity(intentAddEdit1);
                break;
        }
    }
}

LogCat-

造成原因：

 java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.util.ArrayList.add(java.lang.Object)' on a null object reference
        at com.itschoolsamsung.myapp.ContactActivity.onCreate(ContactActivity.java:36)

我究竟做错了什么？

Answer 1

您尚未初始化联系人数组列表

用这个

private ArrayList<String> contacts =new ArrayList<String>();