java – TEXTVIEW证实地点

所以当用户按下Button1时,Textview字段提供“你按下了Button1”

我的问题是关于正确的地方,我可以实例化Textview ONLY ONCE,因为唯一的工作地点是在Button1函数内.

单个按钮的Java代码：

public void Button1(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);
        textView.setText("You clicked the button 1");

    }

总java代码

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        FloatingActionButton fab = (FloatingActionButton)   findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view,"Replace with your own action",Snackbar.LENGTH_LONG)
                        .setAction("Action",null).show();
            }
        });


    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main,menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button,so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public void Button1(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);
        textView.setText("You clicked the button 1");

    }
    public void Button2(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);

        textView.setText("You clicked the button 2");
    }
    public void Button3(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);

        textView.setText("You clicked the button 3");
    }
    public void Button4(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);

        textView.setText("You clicked the button 4");

    }
    public void Button5(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);

        textView.setText("You clicked the button 5");
    }
    public void Button6(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);

        textView.setText("You clicked the button 6");
    }
}

总XML代码

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/RelativeLayoutID"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.sherifsaleh.xmllayout.MainActivity"
    tools:showIn="@layout/activity_main"
    >

    <Button
        android:id="@+id/button3"
        android:onClick="Button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="3"
        android:layout_above="@+id/button6"
        android:layout_alignLeft="@+id/button6"
        android:layout_alignStart="@+id/button6" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="Button6"
        android:text="6"
        android:id="@+id/button6"
        android:layout_below="@+id/button2"
        android:layout_alignLeft="@+id/button9"
        android:layout_alignStart="@+id/button9" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="9"
        android:id="@+id/button9"
        android:onClick="Button9"
        android:layout_alignTop="@+id/button8"
        android:layout_toRightOf="@+id/button8"
        android:layout_toEndOf="@+id/button8" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="8"
        android:id="@+id/button8"
        android:layout_below="@+id/button5"
        android:layout_toRightOf="@+id/button4"
        android:layout_toEndOf="@+id/button4"
        android:onClick="Button8"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="2"
        android:onClick="Button2"
        android:id="@+id/button2"
        android:layout_above="@+id/button5"
        android:layout_toRightOf="@+id/button1"
        android:layout_toEndOf="@+id/button1" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="Button5"
        android:text="5"
        android:id="@+id/button5"
        android:layout_below="@+id/button1"
        android:layout_toRightOf="@+id/button1"
        android:layout_toEndOf="@+id/button1" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="1"
        android:onClick="Button1"
        android:layout_above="@+id/button4"
        android:layout_alignLeft="@+id/button4"
        android:layout_alignStart="@+id/button4" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="4"
        android:id="@+id/button4"
        android:layout_above="@+id/button7"
        android:layout_alignLeft="@+id/button7"
        android:layout_alignStart="@+id/button7" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="7"
        android:id="@+id/button7"
        android:layout_alignParentBottom="true"
        android:layout_alignLeft="@+id/textView2"
        android:layout_alignStart="@+id/textView2"
        android:layout_marginBottom="90dp" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textIsSelectable="true"
        android:text="New Text"
        android:id="@+id/textView2"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="80dp"
        android:textSize="50dp"/>
</RelativeLayout>