<LinearLayout
    android:layout_width="368dp"
    android:layout_height="495dp"
    android:layout_marginTop="8dp"
    android:orientation="vertical"
    android:visibility="visible"
    app:layout_constraintTop_toTopOf="parent"
    tools:layout_editor_absoluteX="8dp">

    <TextView
      android:id="@+id/textView"
      android:layout_width="match_parent"
      android:textSize="@dimen/textsize"
      android:layout_height="wrap_content"
      android:text="@string/text_1" />

    <EditText
      android:id="@+id/editText"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:ems="10"

      android:inputType="number" />

    <Button
      android:id="@+id/button"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:text="@string/text_2" />
  </LinearLayout>

public class MainActivity extends AppCompatActivity {

  private Button btn_call;
  private EditText et_call;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    et_call=(EditText) findViewById(R.id.editText);
    btn_call=(Button)findViewById(R.id.button);
    //为button添加点击事件
    btn_call.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        //取数据
        String number= MainActivity.this.et_call.getText().toString().trim();//trim()方法用来去掉空格
        if("".equals(number)) {
          //土司，提示
          Toast mes = Toast.makeText(MainActivity.this, "对不起，输入不能为空", Toast.LENGTH_LONG);
          mes.show();
        }
        //Intent设置动作和数据
        Intent intent=new Intent();
        intent.setAction(Intent.ACTION_CALL);
        intent.setData(Uri.parse("tel:"+number));
        startActivity(intent);
      }
    });


  }
}