Question

我的java

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.RadioGroup;
import android.widget.Toast;
import android.widget.RadioGroup.OnCheckedChangeListener;
import android.widget.TextView;

public class MainActivity extends Activity{

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

    RadioGroup groupRadio=(RadioGroup)findViewById(R.id.radioGroup1);
    final EditText   squareedt=(EditText)findViewById(R.id.SquareEditText);
    final EditText   reclengthedt=(EditText)findViewById(R.id.RecLengthEditText);
    final EditText  recwidthedt=(EditText)findViewById(R.id.RecWidthEditText);
    final EditText  circleedt=(EditText)findViewById(R.id.CircleEditText);

    final TextView side=(TextView) findViewById(R.id.LabelSide);
    final TextView length=(TextView) findViewById(R.id.LabelLength);
    final TextView width=(TextView) findViewById(R.id.LabelWidth);
    final TextView radius=(TextView) findViewById(R.id.LabelRadius);


    squareedt.setVisibility(View.INVISIBLE);
    reclengthedt.setVisibility(View.INVISIBLE);
    recwidthedt.setVisibility(View.INVISIBLE);
    circleedt.setVisibility(View.INVISIBLE);
    side.setVisibility(View.INVISIBLE);
    length.setVisibility(View.INVISIBLE);
    width.setVisibility(View.INVISIBLE);
    radius.setVisibility(View.INVISIBLE);

    groupRadio.setOnCheckedChangeListener(new OnCheckedChangeListener() {
        public void onCheckedChanged(RadioGroup group, int checkedId) {

          if(checkedId==R.id.rbt1)
          {
              side.setVisibility(View.VISIBLE);
              squareedt.setVisibility(View.VISIBLE);

              float una = Float.parseFloat(squareedt.getText().toString());
              float perimeter = una * una;

              Toast.makeText(this, String.valueOf("The perimeter of square is " + perimeter),Toast.LENGTH_LONG).show();

                length.setVisibility(View.INVISIBLE);
                width.setVisibility(View.INVISIBLE); 
                reclengthedt.setVisibility(View.INVISIBLE);
                recwidthedt.setVisibility(View.INVISIBLE);
                radius.setVisibility(View.INVISIBLE);
                circleedt.setVisibility(View.INVISIBLE);
          }
          else if(checkedId==R.id.rbt2)
          {
            length.setVisibility(View.VISIBLE);
            width.setVisibility(View.VISIBLE); 
            reclengthedt.setVisibility(View.VISIBLE);
            recwidthedt.setVisibility(View.VISIBLE);
              side.setVisibility(View.INVISIBLE);
              squareedt.setVisibility(View.INVISIBLE);
              radius.setVisibility(View.INVISIBLE);
              circleedt.setVisibility(View.INVISIBLE);
          }
          else if(checkedId==R.id.rbt3)
          {
              radius.setVisibility(View.VISIBLE);
              circleedt.setVisibility(View.VISIBLE);

              length.setVisibility(View.INVISIBLE);
                width.setVisibility(View.INVISIBLE); 
                reclengthedt.setVisibility(View.INVISIBLE);
                recwidthedt.setVisibility(View.INVISIBLE);
                  side.setVisibility(View.INVISIBLE);
                  squareedt.setVisibility(View.INVISIBLE);
          }
        }
    });
}



}

我总是遇到这个代码的问题

    Toast.makeText(this, String.valueOf("The perimeter of square is " + perimeter),Toast.LENGTH_LONG).show();

错误是这样的; Toast类型中的方法makeText（Context，CharSequence，int）不适用于参数（new RadioGroup.OnCheckedChangeListener（）{}，String，int）

我的xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/RelativeLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.cell.phone.MainActivity$PlaceholderFragment" >

<RadioGroup
    android:id="@+id/radioGroup1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true" >

    <RadioButton
        android:id="@+id/rbt1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/square" />

    <RadioButton
        android:id="@+id/rbt2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/rectangle" />

    <RadioButton
        android:id="@+id/rbt3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/circle" />
</RadioGroup>


<TextView
    android:id="@+id/LabelSide"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/radioGroup1"
    android:layout_below="@+id/radioGroup1"
    android:layout_marginLeft="15dp"
    android:layout_marginTop="22dp"
    android:text="@string/side"
    android:textAppearance="?android:attr/textAppearanceLarge" />

<EditText
    android:id="@+id/SquareEditText"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/LabelSide"
    android:layout_alignBottom="@+id/LabelSide"
    android:layout_marginLeft="16dp"
    android:layout_toRightOf="@+id/LabelSide"
    android:ems="10"
    android:inputType="number" >

    <requestFocus />
</EditText>

<EditText
    android:id="@+id/RecLengthEditText"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/LabelSide"
    android:layout_alignBottom="@+id/LabelSide"
    android:layout_marginLeft="16dp"
    android:layout_toRightOf="@+id/LabelSide"
    android:ems="10"
    android:inputType="number" />

<TextView
    android:id="@+id/LabelLength"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/LabelSide"
    android:layout_alignBottom="@+id/LabelSide"
    android:layout_alignLeft="@+id/radioGroup1"
    android:text="@string/length"
    android:textAppearance="?android:attr/textAppearanceLarge" />

<EditText
    android:id="@+id/RecWidthEditText"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/SquareEditText"
    android:layout_below="@+id/SquareEditText"
    android:ems="10"
    android:inputType="number" />

<TextView
    android:id="@+id/LabelWidth"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/RecWidthEditText"
    android:layout_alignBottom="@+id/RecWidthEditText"
    android:layout_alignLeft="@+id/radioGroup1"
    android:text="@string/width"
    android:textAppearance="?android:attr/textAppearanceLarge" />

<EditText
    android:id="@+id/CircleEditText"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/LabelSide"
    android:layout_alignBottom="@+id/LabelSide"
    android:layout_marginLeft="16dp"
    android:layout_toRightOf="@+id/LabelSide"
    android:ems="10"
    android:inputType="number" />

<TextView
    android:id="@+id/LabelRadius"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/LabelSide"
    android:layout_alignBottom="@+id/LabelSide"
    android:layout_alignLeft="@+id/radioGroup1"
    android:text="@string/radius"
    android:textAppearance="?android:attr/textAppearanceLarge" />

<TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/RecWidthEditText"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="46dp"
    android:gravity="center_vertical|center_horizontal|center"
    android:text="" />

Answer 1

变化：

Toast.makeText(this, String.valueOf("The perimeter of square is " + perimeter),Toast.LENGTH_LONG).show();

要：

Toast.makeText(MainActivity.this, String.valueOf("The perimeter of square is " + perimeter),Toast.LENGTH_LONG).show();

this此处引用的OnCheckedChangeListener不适用于makeText(Context, CharSequence, int)。 MainActivty.this是上下文。

Answer 2

尝试替换

 Toast.makeText(this, String.valueOf("The perimeter of square is " + perimeter),Toast.LENGTH_LONG).show();

通过

Toast.makeText(getApplicationContext(), "The perimeter of square is " + perimeter,Toast.LENGTH_LONG).show();

OR

Toast.makeText(MainActivity.this, "The perimeter of square is " + perimeter,Toast.LENGTH_LONG).show();

如何使用Toast显示计算的周长

2 个答案: