试试这段代码

final EditText editText = findViewById(R.id.name); // your edittext id in xml
Button submit = findViewById(R.id.submit_button); // your button id in xml
submit.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) 
    {
        String string = editText.getText().toString();
        Toast.makeText(MainActivity.this, string, Toast.LENGTH_SHORT).show();
    }
});

我猜你在调用EditText对象“mEdit”时必须使用这段代码:

.toString myActivity.this.mEdit.getText () ()

只需确保编译器知道要调用和使用哪个EditText。

使用getText():

Button   mButton;
EditText mEdit;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    mButton = (Button)findViewById(R.id.button);
    mEdit   = (EditText)findViewById(R.id.edittext);

    mButton.setOnClickListener(
        new View.OnClickListener()
        {
            public void onClick(View view)
            {
                Log.v("EditText", mEdit.getText().toString());
            }
        });
}

    Button kapatButon = (Button) findViewById(R.id.islemButonKapat);
    Button hesaplaButon = (Button) findViewById(R.id.islemButonHesapla);
    Button ayarlarButon = (Button) findViewById(R.id.islemButonAyarlar);

    final EditText ders1Vize = (EditText) findViewById(R.id.ders1Vize);
    final EditText ders1Final = (EditText) findViewById(R.id.ders1Final);
    final EditText ders1Ortalama = (EditText) findViewById(R.id.ders1Ortalama);

    //

    final EditText ders2Vize = (EditText) findViewById(R.id.ders2Vize);
    final EditText ders2Final = (EditText) findViewById(R.id.ders2Final);
    final EditText ders2Ortalama = (EditText) findViewById(R.id.ders2Ortalama);
    //
    final EditText ders3Vize = (EditText) findViewById(R.id.ders3Vize);
    final EditText ders3Final = (EditText) findViewById(R.id.ders3Final);
    final EditText ders3Ortalama = (EditText) findViewById(R.id.ders3Ortalama);
    //
    final EditText ders4Vize = (EditText) findViewById(R.id.ders4Vize);
    final EditText ders4Final = (EditText) findViewById(R.id.ders4Final);
    final EditText ders4Ortalama = (EditText) findViewById(R.id.ders4Ortalama);
    //
    final EditText ders5Vize = (EditText) findViewById(R.id.ders5Vize);
    final EditText ders5Final = (EditText) findViewById(R.id.ders5Final);
    final EditText ders5Ortalama = (EditText) findViewById(R.id.ders5Ortalama);
    //
    final EditText ders6Vize = (EditText) findViewById(R.id.ders6Vize);
    final EditText ders6Final = (EditText) findViewById(R.id.ders6Final);
    final EditText ders6Ortalama = (EditText) findViewById(R.id.ders6Ortalama);
    //
    final EditText ders7Vize = (EditText) findViewById(R.id.ders7Vize);
    final EditText ders7Final = (EditText) findViewById(R.id.ders7Final);
    final EditText ders7Ortalama = (EditText) findViewById(R.id.ders7Ortalama);
    //

    /*
     * 
     * 
     * */

    kapatButon.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // kapatma islemi
            Toast.makeText(getApplicationContext(), "kapat",
                    Toast.LENGTH_LONG).show();
        }
    });
    /*
     * 
     * 
     * */
    hesaplaButon.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // hesap islemi

            int d1v = Integer.parseInt(ders1Vize.getText().toString());
            int d1f = Integer.parseInt(ders1Final.getText().toString());
            int ort1 = (int) (d1v * 0.4 + d1f * 0.6);
            ders1Ortalama.setText("" + ort1);
            //
            int d2v = Integer.parseInt(ders2Vize.getText().toString());
            int d2f = Integer.parseInt(ders2Final.getText().toString());
            int ort2 = (int) (d2v * 0.4 + d2f * 0.6);
            ders2Ortalama.setText("" + ort2);
            //
            int d3v = Integer.parseInt(ders3Vize.getText().toString());
            int d3f = Integer.parseInt(ders3Final.getText().toString());
            int ort3 = (int) (d3v * 0.4 + d3f * 0.6);
            ders3Ortalama.setText("" + ort3);
            //
            int d4v = Integer.parseInt(ders4Vize.getText().toString());
            int d4f = Integer.parseInt(ders4Final.getText().toString());
            int ort4 = (int) (d4v * 0.4 + d4f * 0.6);
            ders4Ortalama.setText("" + ort4);
            //
            int d5v = Integer.parseInt(ders5Vize.getText().toString());
            int d5f = Integer.parseInt(ders5Final.getText().toString());
            int ort5 = (int) (d5v * 0.4 + d5f * 0.6);
            ders5Ortalama.setText("" + ort5);
            //
            int d6v = Integer.parseInt(ders6Vize.getText().toString());
            int d6f = Integer.parseInt(ders6Final.getText().toString());
            int ort6 = (int) (d6v * 0.4 + d6f * 0.6);
            ders6Ortalama.setText("" + ort6);
            //
            int d7v = Integer.parseInt(ders7Vize.getText().toString());
            int d7f = Integer.parseInt(ders7Final.getText().toString());
            int ort7 = (int) (d7v * 0.4 + d7f * 0.6);
            ders7Ortalama.setText("" + ort7);
            //




            Toast.makeText(getApplicationContext(), "hesapla",
                    Toast.LENGTH_LONG).show();
        }
    });

最短和最简单

getText（editText）;

获取文本（按钮）;

getText（textView）;

一些解决方法

只要在你的BaseActivity中创建方法，如果你没有的话。

public class BaseActivity extends AppCompatActivity{
    public String getText(TextView tv) {
        return tv.getText().toString().trim();
    } 
}

并通过这个BaseActivity扩展你的所有活动。

public class YourActivity extends BaseActivity {
  @Override
  public void onCreate(Bundle savedInstanceState){
     getText(editText);
     getText(button);
     getText(textView);
  }
}

注意，EditText，按钮扩展TextView，所以我只创建getText(TextView电视)。

字符串值= YourEditText.getText().toString;