有這樣的代碼，里面的String.format("%d", progress)是什么意思？為什么要這么寫？%d是什么？package com.example.seekbar;import android.app.Activity;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.widget.SeekBar;import android.widget.SeekBar.OnSeekBarChangeListener;import android.widget.TextView;public class MainActivity extends Activity {private SeekBar seekBar1;private TextView textView1;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);seekBar1=(SeekBar)findViewById(R.id.seekBar1);textView1=(TextView)findViewById(R.id.textView1);seekBar1.setMax(100);seekBar1.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {@Overridepublic void onStopTrackingTouch(SeekBar seekBar) {// TODO Auto-generated method stub}@Overridepublic void onStartTrackingTouch(SeekBar seekBar) {// TODO Auto-generated method stub}@Overridepublic void onProgressChanged(SeekBar seekBar, int progress,boolean fromUser) {textView1.setText("音量："+String.format("%d", progress)+"%");}}) ;}}