android studio 在MainActivity中添加几个按钮实现发送短信的功能

首先，在MainActivity布局文件中添加几个按钮，例如：

<Button
    android:id="@+id/btn_send_sms"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Send SMS" />

<Button
    android:id="@+id/btn_choose_contact"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Choose Contact" />

<EditText
    android:id="@+id/edit_text_sms"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:hint="Enter your message" />

然后，在MainActivity中添加代码实现发送短信的功能：

public class MainActivity extends AppCompatActivity {

    private static final int PICK_CONTACT_REQUEST = 1;

    private EditText mEditTextSms;

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

        Button btnSendSms = findViewById(R.id.btn_send_sms);
        btnSendSms.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                sendSms();
            }
        });

        Button btnChooseContact = findViewById(R.id.btn_choose_contact);
        btnChooseContact.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                chooseContact();
            }
        });

        mEditTextSms = findViewById(R.id.edit_text_sms);
    }

    private void sendSms() {
        String message = mEditTextSms.getText().toString();
        if (!TextUtils.isEmpty(message)) {
            Intent intent = new Intent(Intent.ACTION_SENDTO);
            intent.setData(Uri.parse("smsto:" + ""));
            intent.putExtra("sms_body", message);
            if (intent.resolveActivity(getPackageManager()) != null) {
                startActivity(intent);
            }
        }
    }

    private void chooseContact() {
        Intent intent = new Intent(Intent.ACTION_PICK, ContactsContract.Contacts.CONTENT_URI);
        startActivityForResult(intent, PICK_CONTACT_REQUEST);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == PICK_CONTACT_REQUEST && resultCode == RESULT_OK) {
            Uri contactUri = data.getData();
            String[] projection = {ContactsContract.CommonDataKinds.Phone.NUMBER};
            Cursor cursor = getContentResolver().query(contactUri, projection, null, null, null);
            if (cursor != null && cursor.moveToFirst()) {
                int numberIndex = cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER);
                String number = cursor.getString(numberIndex);
                mEditTextSms.setText(number);
            }
            if (cursor != null) {
                cursor.close();
            }
        }
    }
}

其中，sendSms()方法实现发送短信的功能，chooseContact()方法实现选择联系人的功能。在onActivityResult()方法中获取选择的联系人的电话号码，并将其填充到EditText中。